Does not recommend this product
Don't put 'FREE' everywhere if it's actually paid and the only thing you get for free is a low-res png, which is practically unusable. Also the number of illustration is currently very low and charging 10-20$ each is not a good idea. It would be better if you group illustrations into packs and charge 10-20$ or whatever price for the whole pack and give 1 or 2 illustrations from the pack for free in hi-res format.