I had EXACTLY the same problem as you!
My venue had beautiful wood-panelled walls… …which were littered with light switches, emergency exit signs, and pictures of birds which were, get this, NAILED to the walls. They also didn’t allow anything to be stuck into the walls, so draping was a no-no. It also gets VERY expensive, and our venue had a serving hatch and loads of windows and doors, so draping would have looked ridiculous.
I posted my exact same problem on a different site and was just told “don’t worry, everyone will be having such a good time they won’t notice”, and discounted it immediately. But honestly, it’s true. We wound up running out of time to do anything about it so we left it as it was, and our photographer was able to edit them out so that you wouldn’t even know they were there.
But here’s some options for you:
1. Find out the size of the pictures and make your own that size. Maybe pictures from your engagement shoot, if you had one? You can just stick them to the pictures with double-sided tape on the back and no one will notice.
2. Turn them into signature frames! All you’ll need is a piece of card or paper the same size as the frame, and then a smaller picture to go in the middle. Obviously, you may have some that are blank (with them being all over the walls, some people may not realise that’s what they’re for, or there may just be too many to be fully filled) but at least it will look good.
3. Planning. Arrange your reception around them. E.g: don’t have your cake table right in front of one, ot they’ll be in all the pictures of the cake cutting and it’ll draw your guests’ attention to them. Ditto first dance, top table, favour table, etc.
4. Turn them into mirrors. Like with the pictures, you can get mirrored plastic and stick it on there!
Honestly, it could be worse. At least you can take them down! Our venue had them NAILED in!
If you’re comfortable with this, send me a PM with your email address and I’ll show you pictures of our venue before the day and on the day, and then edited with the ugly pictures removed. You’ll be amazed how you just don’t notice them when your room’s decorated (in fact, I just looked at the ‘before’ picture out of curiousity, and thought “wow, was it REALLY that ugly?”: I totally forgot all about them!).