You may find some answers at the WC WiKi found here. http://wiki.wincustomize.com/wiki/Main_Page I'm a casual user of graphics and rely on PaintDotNet to do my small amount of graphics work.  You'll find that the various artists who create skins use PhotoShop and other similar programs for their actual graphics work.

If you're already familiar with the graphics programs and use them now then you could probably tackle right away a full Window Blinds skin but, if you're just learning graphics software now start with something smaller an icon, a right click skin an Object Dock skin or something else that suits you.  A full Window Blinds skin is a big project.  Beyond my limited skills.

You also find there is plenty of help available.  I'm expecting right now many artists will be busy with GUI championship projects and may seem scarce but, be patient you'll get your chance to jump in the pool soon enough.

This might be a good place to start:

https://www.wincustomize.com/Articles.aspx?AID=136983

There are tons of them out there. Google 'Photoshop Tutorials' and you will find enough of them to keep you busy for a long time!

Thanks for the ideas! I downloaded paint.net yesterday and so far I've created a couple glass buttons and made a fire background! It's so easy to use and their tutorials are great! Thanks Bichur!

There is a freeware program called The Gimp.....very similar to Photoshop, just not as many goodies to it, and plenty of tuts out there for it as well. I have found that I don't do so well with tuts....I have a tendancy to go off in another direction....dang ADD . I guess that is why I haven't moved on from doing walls....woe is me.