Venue wall is plain

If you don’t like the idea of draping, you could do a string light wall. Either plain lights, or you could add greenery, flowers, sheer, drapings, etc.
Depending on your budget, you could also rent props (something like the last two pictures).
Or you could leave the sides empty and create a really nice focal point in the middle where you will be standing (like a flower arch, or draping, etc) Most photos will be cropped anyway.

I would go with a really dramatic floral arrangement on a pedestal on either side of the altar (halfway between the aisle and the corner). I will come back with inspo pics

View Quoted Comment These are really cute! Thank you so much
I’m thinking of mixing the our idea of lights and floral

Some floral ideas:

Is this for the ceremony or reception or both? A super cheap idea that has big effect is to get plain clear Christmas lights (don’t pay the up charge for them being wedding lights with white wires and no one will notice or care what color the electrical wrapping on the strings are) and hang them from the ceiling. You can use heavy duty command strips which won’t damage the paint underneath.

Also guests do understand that venues are out of your control as far as walls, ceilings, floors, etc. People generally don’t care that a wall is plain nor do they expect you to have a Kardashian budget and aesthetic to cover it because it’s a wedding. Keep it simple and people will focus on the details that matter: having a good time.

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People generally don’t care that a wall is plain nor do they expect you to have a Kardashian budget

YES YES YES YES and can I say "YES" again? I absolutely HATE that so many wedding sites push the "over the top" decorations. THOUSANDS of dollars for a half hour out of the day??? Nooooo. Spend it on the quality of the food, please!

Agreed that the wall will not be a bit issue. Some options are available though. You could put up a folding room divider on each side. Possibly have colored lights shining up the wall --which might be nice if the room lights are dimmed around that wall. It may be possible to hang sheets, drapes or wedding-themed sign on some improvised frame on both sides. These frames could be of pvc pipe for do-it-yourself people. I'm thinking mainly where the venue lacks any spots where you can affix a wire or support point for a sign or drapes

I think the wall is fine. It being plain draws the focus to the center, where the important stuff is!