Do you mean other gouramies or just any other fish?
If you mean just any other fish, something mid-dwelling and shoaling would probably look best. Maybe some harlequin rasboras or checker barbs or you could try a school of black phantom tetras. The rasboras are the closest schooling but I always think black phantoms look stunning with pearls because they compliment them so well in terms of fin shape and colors. Other schooling fish you could consider are spotted rasboras, glowlights, neons, cardinals, congo tetras, silver-tipped tetras, neon blue/dwarf/paecox rainbowfish, pristella (x-ray) tetras, clown rasboras, threadfin rainbowfish (I think these are gorgeous) or pretty much any other non-nippy shoaling fish that won't get to large (so as not to overstock as they need to be in a gorup of 6).
You may notice I didn't mention any danios - I absolutely LOVE danios but, unfortunately, the most common species such as zebra or pearl also like the top layers. As such, coupled with their high activity level, they are not ideal pearl tankmates. Having said that, if you can get some of the smaller, rarer species, you could keep a group of those as well.
Another to cosnider might be pygmy/dwarf cories. Those tend to spend their time in the mid-lower region of the water column so make good shoaling fish, though unconventional, for a gourami tank.
You could also get a trio of cherry barbs, platies, guppies, endler's, american-flag fish or swordtails. Avoid mollies - for some reason they just don't usualy get on with gouramies - I think it's probably because they tend to spend a lot of time in the upper water layers and get relatively large so they often clash with gouramies. Obviously, none of these are schooling fish (note - cherry barbs don't school) but a trio of any of these would work nicely together with the pearls. Do watch you don't mix endler's with guppies and remember that livebearers need to either be in a single-sex group (in which case you need not go for a trio) or in groups with at least 2 females per male (arguably more females are needed with male guppies).