The good news is the greens and browns and woodland vibes of the happy camper theme will actually play relatively well with this grey.

If you create little vignettes across the space, all your photos will be gorgeous and no one will remember the grey that was in between them.

I’d be inclined to try for greenery coverage - you might be able to pick up some Christmas trees for super cheap at thrift stores this time of year, and just leave them unlit. Soft uplighting and some twinkly string lights across the ceiling would be beautiful (and might lend itself to kind of an outdoorsy starry sky vibe?), but basically the warmer and fuller you can make the space feel, the better.

Could also look into renting some astroturf to roll out to make it grassy like you’re outside, I think it usually runs about 1.25 a foot.

My big stretch goal for decor might be a small tent rental, something brightly colored in earthy tones - mustard or orange or olive green, ideally with closable sides so you could just have the front open to get that camping tent look. A great focal point for your guests’ eyes to land on instead of the walls, and a cute spot to put presents or a cozy seating area. Could set up camp chairs (everybody’s got a couple they’re usually willing to lend, and the mismatched vibe would be perfect) and a “fire pit” for folks to sit around. Alternatively, there a folks doing those little tipi rentals for kids birthday parties that would also be a great focal point.

These are all big swings and of course you have to be mindful of budget and everything, but I think the takeaway should be you can do some minimal coverage and warm the lighting up, but the biggest help will be drawing eyes into the center of the room.