Some great ideas here!
A few of us at one of the homes I worked at used to do a bit before/after shifts or on days off because we were usually too busy caring on shift (as in we did it for free in our own time because there wasn't an activity budget so we had to fundraise too) places are normally better these days with activities, but a few things we did were -
A Wii connect with different games - it took some help obviously but most of our residents loved it once they made the connection between the screen character and their movements.
A beer tasting club, you buy different beers each week/ month and then make up score cards for taste, smoothness, colour etc and get people to score out of 10, can also do it for wine and even food, and there's loads of non alcoholic drinks available these days if alcohol isn't suitable for some people.
A 'family' tree - where you take a blank wall and make a trunk/branches out of cardboard and stick it on the wall, then (with permission obviously) pictures and a little sentence about each resident/member of staff. You can also use this for one on one activities (again with permission) for each resident and their families and they have one in their room, you can include pictures etc too.
Bird spotting club with a prize for the person who spots the most.
Another place made 'The Corner' pub in one of the lesser used lounges, an old med cabinet and a juke box type stereo, old pub type tables, beer mats and runners and made pumps out of cardboard and stuck them on the med cabinet for effect and we had cans and wine in the cabinet and 'opened' the pub a few times a week and it was actually quite popular, especially with those who'd been pub goers, they seemed to enjoy the familiarity of coming up to the bar and 'buying' a pint and going back to the table. We had a float of change and we'd give money out when we opened and then take it back in 'payment' so there was no money changing hands.
That was a big project though and was more popular with some than others and the owners were really good as was the activity coordinator.
We had a few people that have been reluctant to join in organised activities, they weren't into clubs etc and had spent their whole lives working or caring for families and so we'd 'ask' for help with things like folding laundry, damp cloth for dusting, organising CDs etc - it really seemed to fulfill people if they thought they were doing something that was helpful rather than 'being entertained' and really helped foster good relationships with the staff and residents.
Also involvement in things like arranging furniture in communal areas, decoration, menu planning - sharing recipes and ideas - really helps people to feel it's their home, not just somewhere they live.