Limited space? Bullshit. Those 6 alone would only add like, what, 120kb? (including the DISBTN) Apparently, DotA players can't handle an extra 4 second download time.
The only gripe I have is that they don't really go well together, there isn't as much of a common theme (for example, the default ones are all red). However, that doesn't make these any less awesome for items, etc.