'aterm -tr' should give me a transparent terminal right??
 

Well, it doesnt... i do aterm -tr and get a black background...

Yes, it should.

Assuming, of course, that you compiled it yourself with the appropriate config flags...

try:
aterm --help
or man aterm ...

it'll give u info about the flags and stuff.. incase the tranparency is not working, try re-compiling!