I'm a fan of the Byzantines as well, but I worry that if you start making graphics this early, you'll be sure to have compatibility issues, either with the filetype you're creating, or with the size, or any number of other issues that won't allow it to mesh easily with Civ 5, you'll be stuck having to fix up or redo the excellent work you've already done.
I hope I'm wrong about this, I don't know much about graphics, but if I'm even a little right you may be better off thinking about general ideas for your Byzantine mod, rather than creating concrete pieces of it, at least until we know how Civ 5 city graphics will function.
I hope I'm wrong about this, I don't know much about graphics, but if I'm even a little right you may be better off thinking about general ideas for your Byzantine mod, rather than creating concrete pieces of it, at least until we know how Civ 5 city graphics will function.