Absolutely! Send photos!
It’s understandable that your new au pair wants to be able to visualize where she is going to be. I think it’s fine to send your au pair some photos of your house, her room, the kids, the closest cafe, etc.
You might also add some links to your town’s website, to the town library, the local counselor’s blog if she has one, and so on. This can be a nice part of on-boarding and orienting your au pair.
Anything that you do to help your new Au Pair get excited about coming to your home helps to amp up the anticipation — and maybe even make it easier for her to leap into the adventure.
The odd part of this request is the language of ‘doing a project for the agency’. I’ve never heard of something like that. I wonder if she’s writing an article on becoming an au pair, or if this is a mis-translation of some other instruction she’s been given. You might want to ask a little more about it, in a conversational way.
The only situation where I’d feel concerned about sending photos is if I felt that the au pair was trying to compare host family situations to see which one was cushier or more glamorous…. Since you have already matched this is probably not what’s going on, so if it were me I wouldn’t worry. But, if you’re bringing this up because you have other concerns, let us know.
All the best, and welcome to the adventure!