i dont ever suggest frogs and bettas. frogs are difficult enough to get to eat regularly without the greedy bettas eating all their food. frogs are slow to sniff out their bloodworms, and we all know bettas cant resist. they will eat until they are too stuffed, and then bad things happen, all the while the frogs dont get their share. id avoid that combination.
and you could have a LOT more than 6 shrimp in a ten gal with a betta (a colony of shrimp of around 60+ would be just fine by themselves). even if you had say six pygmy cories, you could have a lot of shrimp! they add virtually no bioload. again, just make sure they get their share of food. but wait until the tank is cycled and "mature" (around 4 months after cycling) to add shrimp. they are quite sensitive to even small ammonia readings).
i agree some plants (live or silk) and i suppose a hidey hole (although ive tried with every betta ive owned and NONE of them ever used a "cave" or pot).
best of luck.
keep us posted
cheers