No theme. My parties never have a theme. Just a totally clean house, and really good, personally prepared food, the only theme you need IMO. My housewarming was come-and-go, and started around 2 and went til whenever. It was in November.
I have a tiny house, so I started pre-cooking (what would freeze well) in October. I made homemade chocolate nut bars with a crust, chocolate/vanilla checkerboard cookies (serious effort there!), and chocolate biscuits (with homemade bourbon flavored whipped cream made at the last minute). I also did a homemade chocolate pound cake. I pre-cooked a million oven meatballs (party-sized) that I pulled out of the freezer later and put into crock pot with a sauce made of a can of Campbell''s Cream of Mushroom and dry white wine. Cheating a bit, but it''s great stuff, honestly, and EASY!
The day of I made oodles of small crab cakes (from "Miami Spice" cookbook.) with citrus sour cream sauce (absolutely KILLER stuff!). I also pre-marinated 3 pork tenderloins (soy, Worcesteshire, scallions....) that I roasted and served sliced on tiny rolls with various condiments. I also had the pre-made little quiches you can get at Sams. Another cheat. I also had all the major liquors for drinks, mixers, and decent box wines, red and white. The cooking was mostly done when the guests started arriving, so I could have a bunch of fall-scented (Orange and Evergreen, by Aromatique) candles going. Smelled great and looked lovely as the sun went down...
I''m sure I''m forgetting something - it was 11 years ago after all. But it was a huge do I must say. Friends remember it to this day. Our wedding party was a smash too. Did all the cooking myself (with DH this time). We are still getting requests for "another party". But I warn you, it IS a bunch of work, and the way I do it, NOT cheap. Fun though, if you like planning and cooking, which I do.