Sorry for yet another question, but this one just came to me as I started adding the previous topic's fixes to my project. In my original HL1 version of this project, I had "people" standing around that were actually sprites (I opted for sprites rather than brushes because they always face you, making it seem as though they're not just cardboard imitations). I've searched quite a few mapping websites and have not been able to find out if it is currently possible to put custom sprites into the game. My belief is that it should be, since the original game allowed it and it'd be unwise for Valve not to keep such functionality (especially since we have the reality of custom textures/materials/models in Source).
All I'm asking for is if it is possible - if you know anything beyond that, though, like what program I should look for, please let me know.