For FE7, the rolling image is a single one, the same as in the menu. And it can be different if you change the right pointer like Rex did. The frame which goes around the text is actually a moving image, and in theory it still exists in the FE8 model(Even though in FE8 they made that layer become the shinny thingie layer, so importing it would take a while. The tiles are still loaded, however, even in FE8...for sheer laziness I take it. ...in theory you could do something with them I guess. XP)
Also for Battle Templates, 16 colors on each side, including colors for all texts but hit/dmg/crit and HP bars and numbers. Also, FE8 has a bit more space than FE7, both are made of 5 images, and with a limit of say...50? tiles in average in the whole thing, if memory doesn't fail me(Most likely it does)
Inserting one is(Rey can tell you this as well out of experience) a very tiring and demanding job, unless you only plan in a small change of the current model. But something as extensive as the one Lord Glenn has(Sorry, dude.

Also, about a guide, I will indeed consider. ...specially after my guinea-p...err, Rey, had a successful experience with my technique, I might compile it soon enough. It is a pretty cool thing to have in a hack, if you ask me. :3