yay! congrats on gettin a tank together!
there are A LOT of different types of loaches...
http://www.aqualandpetsplus.com/Oddball,%20Loaches.htm
you can go to that site and see a whole bunch of different kinds!
i personally have experience with golden dojos, kuhlis, and clown loaches..
most loaches like to school and behave more happily when in larger groups.. i would recommend getting 2 dojos (these guys do have the potential of getting big tho), or 4 kuhlis (they come in black and "striped") or a combo like ive had.. i had one dojo and 2 kuhlis.. even tho they arent the same type of fish they seemed to school together. i honestly think i have a pick of the 3 in my photo album if u just wanna check em out.
i love kuhlis the most tho just because they are so gosh darn adorable!! i recently bought 2 baby "striped" kuhlis.. they get along great with my adult black ones.. plus they only stay at a max of 3" a piece.. so u can have more of them.
they are great to clean up the gravel when food falls... they tend to "dance" when u put flake in the tank because they smell it and come to join in! very funny!
if u decide they arent for u there are always corydoras as well.. most stay really small and u can get a bunch of them... i have no experience with these fish tho
GOOD LUCK!! heart <3