Hokay, granted I'm the illustrator and my sister's the graphic designer and she has stressed many, many times that illustrators do not have the right mindset when approaching graphic design-- but shit, it's not like I didn't pick up a few things.
Piro's right on the space between the text and the rain lines. You're going to want more space because the eye wants to read the text but the rain lines effectively pull the viewer's eye to the lower right corner of this poster. If I had to suggest a fix, either have the rain stop in the middle or a little above the middle mark of the length of the poster and have the text at the bottom so the rain lines pulls the eye down the poster and gives the viewer the chance to process the information on it. You could either keep everything very solid, or have the rain lines slowly become transparent the closer they get to the middle mark-- what's more important? The text or the the fact that there's rain coming out of the gray clouds?
The dancing couple is a very nice touch but I'm with Diana, the couple should either be an entirely different shade (darker, I think would work nicely) and maybe have them off to the right side since that's where the rain is falling. But you know, having the rain fall with a softer incline would have the same effect and wouldn't be such a drastic element to your design. It's understood that gray clouds have rain and that the rain will be falling on these dancers and be very "Dancing in the Rain". The point of graphic design is to convey a message with eye-catching visuals but not have them be -so- interesting that they detract from the message. It's a hard thing to balance... which is why I went for illustration. :D
Now for the typography part of the design. I'd advise playing with font sizes. Everything is the same font, the same size... kind of bores the eye to the point where the viewer opts to concentrate on the rain and completely forgets whatever it is being advertised. Since the cloud, rain and couple is simplistic I'd keep the fonts the same but in order to catch the eye and keep it on the text long enough for the viewer to ask whether or not they'd like to go dance to Blues music.
Don't get ridiculous with the font sizes for all the text, just remember to account for the where, when and other pertinent contact information. And looking at it, that is a LOT of information to read. So the two options I see is either have the words that talk about the subject matter and use the art to lead the eye to seeing the information that covers the exciting words in big font or your other option is to find a way to reword everything to be more "compact".
And I think the best piece of advice my sister can EVER give in regards to graphic design is thus and I quote her verbatim:
"Papyrus font fucking sucks, don't EVER use it. No graphic designer who knows their shit uses 'papyrus.'"
