A 10 gal is not large enough for any species of Pleco. It is going to quickly outgrow the tank, I would take it back to the place you got it from.
You could get some of the smaller species of cory cats like the panda cory, or pigmy corys. They do bet on a sand substrate so that their barbels do not get damaged and they are a shoaling species so you'll need at least 6 of them to keep them feeling secure.
Harlequin Rasboras are also nice, they are schooling fish and you'll need 6 or more of them.
If you are at least a month after cycling, and your tank is heavily planted, then you could try shrimp,
Snails can also make good tank mates, just be aware that most do reproduce but you can control the rate they do so by not feeding them much. If you get nerites they only eat live algae, no algae and they starve to death.