I would recommend going to a good fish store and seeing what appeals to you. Anyone making recommendations would be telling you what they would like to keep, not what you should keep.
Based on what you have said a small group of cory catfish would go well in a 29g tank. A small species of cory like panda corys maybe. These will help with keeping your tank clear of uneaten food by foraging around on the substrate.
If you like armoured fish a small pleco could go in there too. Bristlenose plecos stay small enough for your tank size and are usually available in decent fish stores. Other smaller plecos like pitbull or clown plecos may be available. Plecos are good algae eaters and will help keep your glass and any decorations clean. If you get a pleco make sure its a species that stays small. For example "common plecos" may only be a couple of inches in the store, but grow into big fish and would easily need a 100+ gallon tank.
I would look at a decent sized group of social fish to fill out the tank. Tetras come in all shapes and sizes, they are normally quite peaceful. Danios can be a more active fish and are fun to watch zooming about the tank. If you wanted something more aggressive/ semi aggressive maybe some barbs like tiger barbs or odessa barbs.
Or there are livebearers. Guppies, platys, mollys and swordtails are good in community tanks. If you want livebearers and dont want to get overrun with babies make you get a single sex.
If you wanted a centrepiece fish there are a few options. If you have other non aggressive fish you will probably get away with a betta. Or maybe a gourami. A 29g is just about what you would get away with an angelfish in.
Play about with ideas here.
https://aqadvisor.com/
It will raise any compatibility issues between different fish you might want to keep, and ensure you dont overstock the tank and filtration.
