How about a background that looks like a YouTube screen.
Or one that's is an interpretation of a blog, with a guy sitting in the middle so that when you place the speech bubble either side of his head it's like we are reading what he has blogged. You kids are still calling them blogs right? I didn't just make that word up did I?
How about some sort of Land of the Giants set?
How about a garage. You know, the sort of place where kids might play hacky/footbag
Or a lab with two giant pods filled with green bubbling liquid with some sort or creatures inside, again the speech bubble could be used with just the background alone.
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GOVT. Warning: Do not smoke around children they will badger you for fags.