We have the 4x4 unit (so 16 shelves) for DD's toys and have 4 of the red (clearish) tubs running on a diagonal. It looks great and works brilliantly.

I keep various things in the 4 tubs - one has her full farm set, another musical interments, another has shape sorters and stacking cups (and other similar toys) and the other is random. Lol!

In the exposed shelves I have a couple filled with books then other toys displayed the remaining shelves. I get comments on it all the time and a few friends have done the same with their kids play area.

We initially looked at getting a more modern basket to use but the woven ones we liked had a really over powering smell and the material ones didn't look 'fun' enough. The plastic ones are great as you can see into them and they fit perfectly. It looks fab in the corner of our lounge at the moment too as we have chocolate furniture (so the unit is chocolate too) with red, brown and orange accessories (earthy tones) so the red fits in well.

Love them!!