I'm not as familiar with the CE, but you should still be able to make sprites with individual pixels or lines and for commands. If the speed is comparable to the TI-84+, this will be (relativley)slow. You can use asm libs, but that wouldn't be pure BASIC. If I remember right, there's a version of Xlib out there for the CE, and maybe something else. The 84+ also had Dual layer Ascill that could be done, but I think saving and storing pictures is a bit different on the CE and that causes this not to work (someone more knowledgeable would have to verify). There are other techniques that were used on the 84+ using text to make sprites, but they are limited on what they can produce, and again I'm not sure if or how well they work on the CE. Here's a link describing some of these from TIBD.
http://tibasicdev.wikidot.com/graphics As I said this applies to the 84+/83+ line, and I'm not sure how relevant it is to the CE.