How about wiggling your fingers?
can be used, or
How about that you wiggle your fingers?
is also OK, and the that can be omitted, leading to
How about you wiggle your fingers?
and in conversation, sometimes the subject can be omitted because of conversational elision, so you might hear How about wiggle your fingers?, but I would avoid writing that and even saying that unless the subject is clear from context.
But really the infinitive doesn't follow after how about when it is used like this - if you hear just the plain form of the verb, usually the subject should have been there but it was omitted.
But, it is possible to use the infinitive and to will be needed - consider this contrived example:
I found this tool. I don't know what it's used for.
That's a strange tool. Could it be used to fix broken windows?
No, but how about to fix broken doors? I bet it that's it's purpose.
How here is closer to it's literal meaning of in what manner, but you couldn't substitute in what manner when presenting alternatives to Do you want to X? How about Y?.