The fact you mention LGPL means you're probably using SDL 1.2, because SDL2 switched to zlib. Just remarking. You can still try to see if you can get an exception though, I know several SDL 1.2 games on iOS got an exception so they weren't bound to the LGPL.
If I was a much greater programmer, I most likely would be using SDL2, but since it's still deep in development, I decided the solid 1.2 foundation for an engine was the way to go.
Thank you all for the insights, I definitely feel more confident with my intentions, but to dig a little deeper: Selling/licensing a game engine built on software which uses these LGPL and zlib licenses is where I'd find the real hurdles? Now that I've written it out, it seems to make a good deal of sense to me... Why should I benefit financially from the work of a set of lower-level software? Creating a game engine designed to be sold for others to develop with is going to be a big no no here?
The moment I read your post and saw the work I thought to myself, "wow, this is really something." I love the idea, think it's fantastic. The art's wild too, and I've been a huge proponent of all free, all the time, so your choice of tools won me over instantly.
This reminds me, too, about how the idTech5 devkit and toolset works, the old MegaTexture tech and "painting" environments. Big fan of the idea and I hope there's a project out there waiting for your work to get finished!