I will also agree that a peacock, apparently stripped ones get larger, would be fine in a 60G tank. The problem with spiney eels is that there isn't a lot of information out there on them, besides a few common facts. Plus a lot of information is conflicted due to similar appearances in species.
I'll see if I can find the sites I used to read up on that gave decent info on common species, identification help, etc.
As far as mixing other fish, just remember these guys are mainly bottom dwellers, can be shy (so get them first and get them feeding before other fish are added), give them plenty of their own hiding spots, and use sand because they are scaleless and like to burrow. IMO, I would choose a mid-top schooling fish (may act as dither fish), nothing robust or too aggressive, so no tiger barbs or spastic species of tetras. I personally would only add a BN pleco for the other bottom dweller. The rest is up to you. I have also read that peacocks like to be in groups, unlike other species, so you could have a pair be the 'centerpiece' fish of the tank. If you don't want to do something like this, you can get a couple other non-aggressive fish. There could be numerous options. At least give us a type of fish you like, color, shape, anything.
Right now i'm growing out a starry night and a zebra with a group of eastern rainbowfish. The starry night is out all the time and the zebra I have to hunt for it to see it. I've never kept zigzags but my peacocks have always been visible most of the time and i've kept them lots of different fish. And yes a stripped peacock could get to large for that set-up as they can reach 18 inches or so.
Well it will definately be a peacock and apparently it is extremely hard to sex them so would it be possible for a pair? Also, I like the idea of a school of medium sized tetras. Either way I am still getting the eel and if it starts to get to big i have no problem in buying another set-up for him.