I started playing around yesterday and I came up with these:

http://img530.imageshack.us/img530/204/mockupdc1.png - full image.
I'm playing with the idea of making an icon theme, probably aimed at gnome, but I've never done this before and so I have no idea what I'm doing! These above are the first mock ups, I thought I'd ask people here what they think and ask a few questions...
1. Do you like them?
2. Does anyone know of a list of all the filetypes/actions/etc/etc that would need to be made?
3. I've read through http://tango.freedesktop.org/Tango_Desktop_Project which seems to make sense (standards, etc) - is this the best style guide to follow?
4. Can anyone critique and suggest improvements to the above mock ups?
5. Which icon style is nicer, the extra glossy one or the others?
6. It'd be pretty cool if I could create a theme that would be implementable across Linux, Windows and OS X - is this possible without three times the work?
7. Would anyone be interested in working on this with me? I'm not looking to spend a large percentage of my time on these each week, I have a lot of other work to do - It'd be more of an informal, spare-time project.
Thanks!