I love the Montessori approach to wall art. Nothing too busy, distracting or overwhelming. Just simple and beautiful.
In children's spaces, I like to use images from nature. It's a part of the Montessori approach to expose the child to reality-based imagery but what is most important to me is that the images are inspiring, uplifting, captivating. I want for my children to see the possibilities of the world, to want to explore the earth, its lands, sky and, oceans.
When Otis was a toddler we used the Bits of Intelligence cards for wall art. They are lovely, the background is white and the images really stand out. The card is thick and glossy (no need for glass in the frame). I love how they looked in Otis' Montessori room. But I ordered the cards from the US and had the frames custom made. I wish I could find the cards locally. So when we moved to the UK I printed some prints from Etsy, which were nice, you can see some here.
But recently I came across the Learning Resources Snapshots. Have you used them? We only have the animal pack. I've tried similar cards previously and have been disappointed in the quality. These are essentially designed to be used like flash cards for critical thinking and language development. They have a series of questions on the back that the teacher (or parent) can ask the student to further discuss the images.
But these cards are excellent quality, not only are they colourful, they are sharp and in focus. The cards are thick and glossy. There is 40 in a pack, which I think is affordable, and great value. But the images... they are all thought-provoking and diverse.
What also makes these so affordable is the cards are 20 cm x 20 cm which mean they fit into a standard 8 x 8 inch frame, which I found easily and very cheaply. I had to slightly trim the cards to fit the frame but only perhaps 1-2mms.
I think these are suitable for all Montessori environments, home and school. Pop in a frame and rotate every so often! Or let the children choose which images they would like to display.
Otto adores the hippo (bottom centre card pictured above) so I think we will need to put that one out soon, or find another frame. They all have rounded corners (which you can't tell once they are in the frame) but they might look ok on the wall as they are.
We also like to use postcards in a wooden frame or stand. There are lots of second-hand books with lovely vintage illustrations and calendars are also worthy of checking out, especially if they are on sale, these all can work well as affordable yet inspiring wall art.