A peaceful community tank is a rewarding way of getting back into the hobby and can make a good visual statement. With the Lido 120 you'll be looking to make use of the height so a top/mid group (11 members) of 3 - 4 cm fish would look good. Depends on your water parameters.
Possible fish (not a complete list):
Tetras, Guppies, Rasboras, Mollies, Pencilfish, Glassfish, Platies, Minnows, Danios, Small Barbs
Sometimes the best place to start is with what fish you want to be the tank boss. Usually this would be larger species that could be kept in pairs of small groups and up to around 6 cm for your tank. Then build the tank and small fish and deco around it. Many of these would dominate the lower level of the tank.
Possible fish:
Gouramies, Apistogrammas, Rams
Then you can add a bit more with snails or shrimp. I only usually add these to serve a purpose. For example, if I want to keep algae in check I'd throw in some Amano shrimp or I have a fish that eats high protein food and I want some help keeping the substrate clear some Assassin snails.
Have a think about if you want a more natural looking aquarium with lots of live plants, wood, and rock or if you want something more decorative with ornaments. Think about what you're putting in and why. A tank full of mixed male guppies and skittle shrimp (a mix of neocardinia davidi of all shiny colours) is one eye catching way to go and makes a bright and bold statement. A shoaling species of fish can be equally as much fun as they zoom around together.
