After reaching the steel age and finishing the story so far in my forever world, I've started building a museum! Since you can display some kinds of skins, antlers, and butterflies, and now fish, as well as artifacts and the like on shelves, cabinets, and on plaques... I've been going wild making different rooms and making the place decorated and pretty and even informational with things like signs and the billposting mod (I used to work at a museum, so it brings me back a bit :] )
Since you have all your survival ducks in a row, you can really take your time making it look cool and fancy. I'm currently painstakingly trying to making a ceiling with a skylight and botanical engravings like some of my favorite museums... with difficulty, I'm not a great chiseler.
Since you're interested in mods, if you do this, things like Fauna of the Stone Age also adds more mounts AND taxidermy, as does the fork of Hieronymus's Reptiles! Catch and Release: Fish can also enable you to make a whole live aquarium, and the reptiles mods could let you fill a greenhouse with live frogs and lizards from different biomes. These should all work on an existing world, too!
