I have to agree with Chloe, the text is weak. Perhaps something simpler without as much contrast in line weight in the letterforms would help (less "thick-thin"). I still dig that rodent illo.... and just the fact that you're trying new things is really good. Keep at it!
OK, well here is the poster I did from what was left from the last poster class assignment. On screen here it's a little hard to read the text on the right, but in physical prints that doesn't seem to be a problem.