Despite my earlier lack of imagination, I'm sure Scooby Doo has the potential to be a fine theme for a pin.
Maybe I was subconsciously having trouble picturing what could be spooky or at least edgy about a Spooky Scooby, seeing as how the show always resolves to everything having a mundane explanation, i.e. not spooky after all. Not in their wheelhouse, as it were. But that's just me overthinking it again, they'd use the pre-explanation ghosts and monsters for the art and it'd be fine.
I don't think including Scrappy Doo would help sales, though. A negative if anything. Didn't everyone hate those episodes?
If they've already hired programmers, it's probably too late to influence their decision, it's already made.