Personally I think larger starfish really need a bigger tank to thrive, I wouldn't include a brittle star in a 60g. If you can find them, micro-brittles are good, but I've never seen anyone sell them direct - I've only occasionally had them come in as hitchhikers.
So that said, here's my opinion as to what you should stock for a clean-up crew:
Conch: For a 60g, you want 2-3 of the smallest conchs. They're essential for keeping the sand bed stirred up and clean. They won't touch glass, but great scavengers.
Astrea snail: I think you want at least 1 per 5g, and you can probably go heavier with them. Personally I favor more diversity in snails rather than going heavy on all Astreas, but you need a small army of these guys. Great for glass cleaning and one of the few CUC members that will directly eat hair algae. Biggest drawback is that they can't right themselves, so you need to either keep your eyes out for them or plan to replenish their numbers regularly.
Cerith snails: You want a mixture of regular and dwarf Cerith snails. They don't have the prolific appetite of Astrea snails, but they're good at tackling a wide mix of algae and their slimmer shells allow them to attack narrower crevices where holdfasts can develop. Also good for glass cleaning. For the dwarfs, 2-3 per 5g; for regular, 1 per 5g is probably good.
Nerites snails: Good general-purpose algae eaters. As with Astrea, probably one per 5g is fine. Make sure you get the tropical species and not the temperate species.
Nassarius snails: Great scavengers. Stick with the smaller species, you want at least one per 10g.
Trochus snails: Everything I said about Astrea is mostly true for Trochus snails, but there are some differences. First, Trochus snails can right themselves, so you don't need to watch out for them as much. On the flipside, they've always seemed more delicate to me; I can keep a population of Astreas in my tank no problem, but whenever I've brought in Trochus they never seem to last past six months, so I don't buy them any longer. Other people have evidently had better luck than I have, so they're definitely worth trying.
Turbo snails: The workhorses. Mexican turbos are pretty common and worthwhile, but personally I'm a big fan of zebra turbos. You can get one Mexican for every 10-15 gallons and they'll do pretty good for you. Zebra, you really only need 1 for every 40-50 gallons. They get huge, and have a correspondingly huge appetite for algae. I have two zebras in my tank (75g); one is the size of a baseball, the other a tennis ball, and they are great at mowing down everything algal.
Urchin: Pincushion or tuxedo urchins are great, and one of the few that will eat coralline algae. That might be a good or a bad thing depending on your personal feelings. Other than that, think of them as a zebra turbo - a little more delicate, a little more hungry.
Hermits: Hermit crabs can be hit or miss. Great scavengers and algae eaters, but they can also go rogue and attack other things, including snails and corals. Some people choose to skip them for that reason. If you want to use them, blue-knuckle, blue-legged and scarlet seem to be the least problematic in my experience. I only keep about 1 hermit for every 10 gallons or so - in small numbers, they seem to behave better. When there are too many of them they tend to get hungrier, and that's when they tend to go rogue.
Finally, and I might attract the ire of the tang police here... A small bristletooth tang makes for an excellent CUC member. At 60g, you might have enough space for one of the smaller bristletooth tangs, such as a tomini.
