[asherkin]

You should use PLATFORM_MAX_PATH rather than picking arbitrary sizes for path buffers.
filename[strlen(filename) - 3] = '\0' is a slightly quicker hack than copying to a new buffer.
While it doesn't really matter, might want to cache the mp_teamlogo_* handles in OnPluginStart().
Not hardcoding the default logos would be better (SM's filesystem functions can read inside the VPK).