Problem is that when checking for collision with one sprite (it's pixel-perfect by the way) I can't tell if part of sprite player is colliding with is spike or harmless object, hence two sprites per chunk - one for harmful things and other for harmless. Supposedly I could do like you are saying, but I'm too much of a n00b yet and I'm basically learning Allegro with this project so...

Also you are talking to guy who barely made world generation and pixel-perfect collision and only because I was given perlin noise unit and was able to (barely) translate pixel-perfect collision code for original Allegro (in C).