I think they look beautiful. You'll need to think about placement so they are not located where your grandson might be tempted to climb up to reach them or even try to climb them, but so they don't look wrongly proportioned for the space. I think shelves are a great idea for photos as you can change them around without all the hassle of measuring and redoing wall hooks, although I have to say I also love a well designed photo wall. Are you wanting to combine photos and other display objects on the same shelf or use specifically photo ledges with a groove for the frames? In the walk-in robe I'd guess you might have various possible solutions apart from floating shelves?

dreamer is right, proper installation is the key. You need good quality shelves attached to studs. I've seen shelves advertised as suitable for attaching to the sheeting but with the proviso that they have less weight capacity. I'd go for attaching to the studs, which means finding them and hoping they are in a position which suits what you want to do. Which is why floating shelves are still on my 'to do' list.

I love the idea of floating shelves! I'm considering installing couple of them in my living room.

Besides the position you need to decide what you'll use the shelves for. If you're planning to store heavier items than just couple of ornaments and photos you need to choose thicker shelving.

Do you know the type of the wall where you'll be installing the shelves? If there are plaster or drywall you may experience some difficulties installing them as these types of walls can crack easily. If that's the case you need to use wall toggles, avoid mounting them directly on the wall.

Good luck!