WishfulPixel, nice work.
Yes, there does seem to be some problem in the composition. It takes a while to latch on to the little guys. Probably because the eye gets drawn in other directions - leading away from them.
The insertion of the pipe is very well executed
(i.e. look as if it were there from the start). The only slight nitpick would be that it seems to be angled slightly upward - which doesn't fit in with the water (? ) flowing out of it.
The little guy, bottom left, seems a little strange. I'm not too well aquainted with frog's front legs - just seems slightly off.
Also there is something near his "backside" - maybe a remnant of the original scene's cut-out?
As to the scale,
unless the guy in the pipe is the "big daddy" frog, then something is awry with the perspective. He's a lot bigger than the others.
Like I said, nice work - I'm just nitpicking.
Rô