Welcome to the forums btj!
If you've bought all the upgrades, no, there's no more upgrades (although you may wish to try to get the cat/dog/turtle, as these could be called upgrades, I guess, if you don't already have them.)
But if you want the game to look different, there are some great mods in the mods section, as Lyssaria said.
And if you think the game is boring, well think again. Here are some good ideas for goals in the game:
Get 50 or 100 generations of peeps.
Get every career (to make it harder, every career to level 8; you may need to write the careers you've had down somewhere, there's a handy list of all the careers in the guides section)
Get all 100 trophies (this is the one I'm working towards with all 5 families).
Get only rare peeps, eg rainbow haired, blue haired, mohawk. These can be found at the bottom of bigheads00.png if you wish to look at them. I know Lyssaria is doing this with one of her families.

Just some ideas! Have fun playing!