How to save Token

Hi everyone! I'm new on roll20 and i've something to ask. I use Adobe Photoshop/Illustrator, depend the time, and i've made few works. But everytime i save them and import on roll20, i lose very very very (and again very) much of quality! The thin lines looks pixeled and the colors are "flat". I tried a lot of size to save (2000,1000,500,400,200,100 PX) But it never look perfect on all zoom. So what format and kind of file do you save your token please? It's this kind of token i want (It's not mine).
Pro For marketplace, generally two to three times the pixels of a unit is expected. Such as for a 1 square token (medium sized D&D creature)... the image should be 210px by 210px so that it looks good when zoomed in.
Thanks a lot for your answer !
Marketplace Creator
Tokens I create I import at 280x280px. They look great up to x4, and if you place them at 1 unit, you can still zoom in on the token to see the detail by highlighting the token and pressing "Z". That token is beautiful BTW!