The characters seem to be at different scales. Maybe drop Frogger altogether, then enlarge Peter Pepper and slightly extend the pyramid so that he is on it rather than floating.
Making Q*Bert smaller and Pac slightly larger would help too. I always kind of imagine Pac and Q*Bert being around the same size, but that Q*Bert is huge, and he is taller than Peter Pepper even, who being a human should be just slightly taller than Pauline.
Or, basic height chart.
Kong and Pauline are both correct.
Peter should be Paulines height or slightly taller. As he is now he is quite a bit shorter, even including his hat.
Pac and Q*Bert should be roughly the same height (they seem to be of a related species of leg and head only creatures). Pac's current height or slightly taller would be about right.
The real problem is Frogger. Is he Frog sized, or is he car sized (in the game he is the same size as the car). Complicating the issue is the fact that the look Frogger has had in the NEW Frogger games has sort of overidden his look from the original cabinet (in my mind at least). I am a classic gamer through and through, but when I think about what Frogger looks like, then he looks like the Frogger on the cover of the Playstation and PC versions. So, basically, not sure if the uninformed even recognize the classic Frogger anymore. The NEW Frogger would be about Pac-Man size I believe. Also, the Frogger graphic you used seems to just be in a different style than the rest of the artwork.