Make shelves the length of the wall, like 1/2 inch thick, and 5-8 inches deep. For the long run you could get some custom built cabinets, which would work amazingly. (Try your local prison or school and see if you could have them made custom for much less)
Change lamp if that's possible
New wall color

Or just make the shelves down one wall but out of your kiddos reach

Remove light. Remove picture over window. You have too much on shelves and they are too high. Add bamboo shade in white to window. Your baby issocute.

A single shelf is a good idea. I suggest presenting your Mickey figures together against a light background ( you might just paint a pair of those you have blue like the walls and put them together), and using lifts for some of them. The rest can hang in colourful mats and frames directly on the walls. As more items enter the scheme, take care not to allow them to overlap with the window treatment borders.

Remove middle shelve and move away from window. Get longer ones and do just 2 on each side.