Black Pearls could also be used for some items

White satin for explorer backgrounds maybe. Even a white marble texture for contrast.

Green foreground, but with transparent taskbar

"Pearl" huh ? .....hmmm....  we´ll see

I would use the first picture i think since it has nice and soft colors.
Iam not a huge fan of all those mineral produkts even if they are part nature.
Most of these things are produced in china in facilities like Lucky Gems or Marvelous industries and there are more.
If you see how these workers House you wouldnt have fun in skinning it well at least i wouldnt even while its a nice idea.
The second picture of the Perlmutt Fossile is just to dark i think.
You could do something equally with Opal wich has a much nicer glow to it its mostly the same to the first picture.
(white opal from Amazonas has some wicked colors.)
Also common opalite would go well with the first picture of yours
http://www.google.de/search?hl=de&q=opalite&bav=on.2,or.r_gc.r_pw.&biw=1796&bih=959&wrapid=tlif130830469146610&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi
you might want to check this link out also http://www.edelopale.de/opale/opalarten-opalisierte-fossilien.html
You can translate the text within iE using bing

Roloccolor it's funny you have mentioned this since I'm crazy about all kind of minerals, gems, rocks etc and I have been colecting some until now. That opalite looks great but unfortunately is synthetic. A true mineral that looks a little bit more like the second picture is Labradorite. That's one of my fav stone.

Pretty. but having readable text and functionality over those type surfaces would be almost impossible.  Good luck with anyone's attempt though.

Yeah mixing those kind of colors it's not for everyone. At least not for those who only can make dark skins with white text. Unfortunately, i'm not either one of those gifted people who can really make a skin like this

I have a head big piece here of Labradorite its indeed a beautifull Gem.
My father was and still is a big fan of gem stones and i think i almost have seen them all in my life.

@ Lightstar i think it would be possible, but like you said hard to achive a good outcome
For example the first picture as startmenu since its already a square shape now a Darkish color for the font would be perfect or an embedded mouseover to make the font more visable 

The Perlmutt picture 2 is to dark and has to many reflections on it to be actually used.
Also the Labradorite picture has to much reflections ( the white spots ) its hard to take good pictures off them since they reflect the light and they only show their color ( blue ) if the light hits them in a good direction hard to explain with my english
Anyway here is a much better shot i think they highlighted that piece from the backside( If this wasnt photographed from the front it would be totally grey )

PS your correct but "opal" isnt synth i just used the opalite to show you how well these soft colors go together ( i think they fit much better than the perlmutt dark colors )
Btw herkimer Diamonds are also synthetic but woman are still into them And opal is much much more expansive than a rough Diamond if its good in quality ^^
Edit: You may also want to look at Larimar or Jasper (even Garnet if its not super good quality and to dark ) Rhodolite and Hematite the list is long these could also go very well with your first picture.
Hope i could provide some tips i  will fav this topic to check back in

I already have a rhodolite and the hematite I will buy it next week from the magazin Treasure of the Earth by Deagostini. They don't sell fake minerals. You must have heard about them I think they sell in your country also.

Here you can see my rhodolite

I wouldn't try even if I could. Way too many variables and controling all of them......I don't know.

yeah rhodolite the pink blackish stone on the right i see you must buy from some manufactures since these are all chips or thumbled stones.
There real good shops that dont sell fake stones all over the world but i never bought any of these i recieved them as present from resellers mostly or i got them from the harvesters directly.
Ps i dont live in the US its easy for me to get my hands on minerals since i currently live near a mineral and gem town located in germany Rheinlandpfalz the city is called Idar-Oberstein and has almost only small buisnesses of mineral shops and lapidarys.
@ Uvah i can imagine what you mean, the only trouble i see so far is the Taskbar itself i can not see a way to make it double taskbar size able with these textures.
also the whole texture would be kinda blurry i think.
But Mr. Paul did it with the element skin as far as i have seen well he is a master.
Deea19 i think you have to find a good color combination of the minerals first and then post what you would like to get.

PS: if you tend to buy from china and be carefull not every mineral is healthy i also got minerals as present that toxic like cinnabarit- Nickelin- Zinnober

Your lucky living near that town. I live in Romania, a country which had many minerals, and still has some, but most of them were exported outside the country back in the '90s   A real crime if you ask me. In Romania most of these minerals and rocks are selled in the fair, but I don't tottaly trust the ones who sell there, nobady will ever admit they sell stones from China, they will probably say they are from Brazil  We don't have many shops that sell these, most of those are selled in Feng-Shui stores, but unfortunately they don't have a large variety of them. So now you can see why I'm buying them from that magazine. Deagostini is pritty well known over the Europe, so I trust them.

Now back to the skin it doesn't have to be entire made with these colors, it might have some black color mixed like this skin

Question do you want the skin to be in the shape of the Penthouse windowblind?
Also what colors do you want for it i think thats the most important.
Example: base color picture 1 from your first post mixed with .............. and black
Iam still working on a skin but when iam finished and no one else decieds to help you out im willing to give it a shot.
But keep in mind im not a master and i´am far from achieving something similar to the Penthouse skin.
PS: I can only skin for windows7 since i have no OS below to test the others.

No I don't want to be similar to Penthouse at all. I was just giving an exemple that ther's no need to be use just one texture, that if it's hard to read the text it can be use black or any other color instead, on that place.

I was thinking more about the first picture I have posted mixed with some dark color and having some shells buttons etc.