This. Someone who is good at making them should explain the best ways to design backgrounds (image dimensions etc), how and where to position text in an OP, stuff like that.
It's hard to write a tutorial just because it's all dependent on what your own vision is—there's no formula.
But for background dimensions the width is 726 px. The height is dependent on how long your post is. Once you get your background on, you can place not only text but images on top as well. Using tables is also very helpful for formatting.
But yeah, the best thing to do is to picture exactly what you want it to look like, and then figure out what exactly is possible to implement on ATRL using just images, text, and tables.
I mean, I'm not trying to say it's perfect because that's vain as hell, but if you look at my Best Of, what I try to do with OP's is keep them simplistic in design but give them something standout and give them some defining quality.
I still use PhotoImpact 7 that I bought for like $100 back in 2001
I should probably buy a more up to date editor sometime soon but I'm still getting my moneys worth :x