Depending on what you are after - i have a few downloadable artworks scattered around here. These may give some inspiration or be a complete pain the ass

Art work for me is always the hardest thing to get right and be happy with.
Just to clarify as i'm not sure you understand the art -> cabinet relationship
You can create art work with any software - hell, you can even do it in MS paint
The real trick is making sure the artwork is the right size - no use creating a master piece that is only A4 in size and doesn't cover your control panel.
I find photoshop great as i create the size from the get go and measure in the components. BUT GIMP is an awesome free alternative and it open photoshop files as well.
Then it is sending the artwork to a printery (quite a few to choose from these days) i use gameongraphix.com as my art comes back exactly at the correct size and colourings.
The printed artwork is printed to an adhesive backed vinyl (like a big old sticker) peal it and stick it on.
Just make sure you prepare the wood surface well - sealed with paint, free from bumps and dust and all that (there are tuts on this somewhere here)
I hope that helps some