Don't have any toy cars yet but I have seen people use those things that use for shoes to hang in wardrobe you know clear plastic front and then a number of pockets - and then hang on the wall, at suitable height for easy access (Might be more suitable for older when want to display the cars though)
we use those ikea tub drawer things. we bought the white 3-stack drawer holder that came with it. works really great (we dont put the lids on...they are packed in the cupboard).
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