Try and draft LKJ from PClinuxOS, I see his work all over the web. He has mad skills when it comes to doing themes.
Hi,
He had done a background that I had used, while trying to make a pclos openbox 64bits (a failure, never worked correctly, due to I don't know what) and at that time he told me that what he did was only backgrounds, nothing else, done fast to please many people and that he didn't like to do anything else.
For themes we need the graphist to do a svg file which he will be able to reuse for different parts of theme, which will be possible for him to pass over to other graphists eventually wishing to rework on it, this in many ways possible. Then for the themes, we need images exported to png. From there we are good to make more.
If you can start with backgrounds in the largest format, for the 2 ratios images said somewhere else... could not remember where so once found I posted a link to dohnston's explanations at tips and tricks.
Ratio of images