As a general rule, all PC DVD creators are crap. I would include Mac programs but I have not tried them. I have concluded that the DVD burner is too new for a killer program to have been released yet. I look forward to the day when I can download a really good free program that will do it better than all the others (alla EAC).
So, sorry, I can't help you there. From what I've seen of the different programs (and I've installed and deleted all of them), they are all very proprietary. However, I don't know how iDVD creates menus, but a program like Impression DVD from Pinnacle uses Photoshop images, but it might require them to be prepared differently.
Argh, now I'm all frustrated again. These programs have really annoyed me for the past few months....