A 10g would make a great shrimp tank or even Scarlet Badis and Red Cherry Shrimp to make it more active and interesting.
For the 45g you could do various rainbowfish since they come in so many colors. My favorite are Iranian Reds and Orange Albino Millinium Rainbowfish. Then Yo-yo loaches for bottom activity. Or 2 angelfish, a school of 10-12 cardinal or rummynose tetras, a dwarf or honey gourami, 6-8 marble hatchetfish for surface schoolers, and 6-8 Cory cats for bottom swimmers.