Lots of leftover cold meats and stuffing.
Bowls of dips like hummus and salsa, with carrot sticks, pepper sticks and bread sticks to dip into them. And some olives in a different bowl, and cherry tomatoes in another.
Things to put into sandwiches - pickles, tomatoes, coleslaw etc
Bowl of green salad.
Cheese and crackers.
Part baked rolls, freshly baked.
Or plan ahead and have the main part of the meal frozen, to just reheat in the oven while you maybe cook some rice/pasta and throw some bowls at the table.
Like a chilli con carne and a vegetarian chilli, served with rice, salsa, tacos, guacamole, crème fraiche, mixed bean salad etc.
Or a lasagna and a veggie lasagna with leaf salad, coleslaw, cherry tomatoes and olives.
For afters, plates of mince pies and brownies, bowl of chocs, cheese board (if not already part of a cold platter), etc, and maybe some ice cream (if you have freezer space, and time ahead of time, you could do what hotels do - let icecream in tub thaw enough to scoop out proper balls and nicely shape them, put onto a tray and refreeze hard, then gently put into a large tub with space between the balls and greaseproof paper between layers - so you just need to serve them but they look impressive on 26th).
In our case, we just throw many packs of M&S party food into the oven as we have a moving feast (some people arrive mid-afternoon and stay a short while, others arrive much later, and some stay until wee small hours - so we just make more as people need it), and plenty of crisps and dips. With pots of mulled wine and many (many) bottles of Lidl's prosecco (very tasty!!).