I'm super excited to design clothes, though I didn't do it as much in WW as I did in GCN and never in CF. I hope to make 18th & 19th century suits and dresses because those were pretty, holiday outfits, and a bunch of cosplays (like Daniel from Amnesia, Count Bleck from SPM, Legend of Zelda characters, etc.). The amount of freedom provided with pants, hat, sock, and shoe choices will make the fashion in this game so complex and personal! :'D
I don't know about furniture patterns yet, but I wouldn't mind designing a Rococo-themed house with lots of intricate swirls. A fun idea would be to do paintings/portaits of the villagers and landscape and display them in the museum as if it were the town's history. I might do that if I have a lot of time (and cute subjects to paint).