Well, it pretty much depends on what system you are using. On linux for example you could use frame buffers (on windows or osx i have no idea). But i think you should check out some kind of library like SDL, which is easy to use and has bindings for common lisp and python (it's written in C).

EDIT: take a look to http://code.google.com/p/lispbuilder/wiki/LispbuilderSDL