I've got a small school of silver dollars in with a small school of clown loaches. In many ways they seem similar and compatible fish. They seem to get along rather well and I believe enjoy similar water parameters. They also both seem rather prone to ich.
SD are very much a schooling fish. They should probably also be kept in groups to see them really come out and relax (much like clowns, just that they have a different idea of "relax" and "cruise"). They could also use the presence of a third placid/dither fish. The SD will (like loaches) observe what other fish are doing and react accordingly. In my own case a group of 3 gouramis (3spot) seem to be the anchor in this respect as they're always out and calm. The SD school around together in the middle/upper parts of the tank and only go down to the bottom with the loaches when I've got an arm in the tank messing with stuff.
SD are very hard on plants, plan accordingly. My original tank (no loaches or SD!) is heavily planted. I'm frequently able to take cuttings and stick them with the loaches/SD. My SD will eat anything, but prefer some things more than others. A leaf of lettuce each day spares most of the things in the tank. Just experiment if possible to find what works for the individuals you end up with.
SD also grow into sizable fish.
Don't let me endorse anything too much (ie take the advice of someone more experienced than me if it conflicts). My case study of a single tank is only so useful.