If you had $1000 for a house project...

Unfortunately, I don’t feel like $1k goes very far. I have recently done the following, which each fell under $1k each, if this helps trigger any ideas for you.
1) Bought two raised, divided planters for our upper deck area and planted herbs in it.
2) Primary bedroom refresh: Replaced a ceiling fan, converted two can lights to pendants, bought some new artwork/decor, and painted the wall behind the bed.
3) Bought bins to organize all of the linen closets in my house.
4) Bought new rugs, planters, and plants for my front porch, and painted the doors (I have two, one to living room and one to mudroom.)
5) Replaced all cushions and pillows (4 hanging swing benches) and the outdoor rug on our lower deck, and also swapped out the decor down there to match.

I am a renter.....so I would do a purchase.

There's a certain cart I want  for my scrapbook area. About $175-ish with tax.
I also want a pantry type cabinet. I have looked at several online, most are around $200-$300.

I'd love to get a new couch.

Replace all your old light fittings with led ones - you can still get natural light but save on your electricity bills etc and they last a long time.
So you spend money but save money😁
OR
I would finally fix that thing in the house that annoys me any time I go near it - for example replace a broken screen door or add an extra electrical outlet in the kitchen or put a light or skylight in that dark dingy hallway/corner where I store all the things etc… so not a major reno but something that would make my everyday life 1000x better.

Our bathroom needs to be repainted (including cabinets and trim) and have some of the drywall patched. That will probably run about $1K. Or I could do it myself, but I don't want to.

replace one window.

New kitchen counter tops and sink.

I am adding board and batton with a 2 inch railing to my dining room. Won't be quite $1000, but I also bought 10 large phot frames as well.

I'd save it for something larger. Just spent a bundle on outdoor landscaping so like to build up savings. But.....to answer you, in your scenario, I'd purchase new dining room curtains, and repaint living and dining rooms.I have a new dining room table and chairs chosen but doesn't meet 1,000.00 budget. I'd maybe consider some new patio furniture if I could get a nice set for 1000.00.

I'd put it towards redoing our patio, new living room furniture or new windows...but it wouldn't likely cover any of those...

A fresh coat of paint can make a huge difference and some new pillows for the sofa or new bedding is nice too

I’m surprised at what you all can do with $1k.
I was thinking “buy a rug”.

I was going to suggest painting as well. We moved here about 10 months ago and the entire house was painted one shade of brown or another. I broke my wrist a month before we moved in and couldn’t paint until January. I painted the living room, hall, entry, and stairway. It took 2 coats of primer and 2 coats of sage green paint, but I LOVE how fresh and clean it looks. 

I was mulling over what my answer would be when I saw this. I love this idea. We have five skylights and they could definitely use a professional cleaning job along with the windows.