I've uploaded a "thumnail" and an "image/flash", but it seems only the thumnail worked. It's very small for an advertisement: https://i.gyazo.com/8cb0673432ae26154d968fe08facf96a.png
Thus, the image for the shop preview becomes very vague: https://i.gyazo.com/58cd4edd049db456953d30bd84074b2a.png
Afterwards, whatever pics, in a valid size, I upload, didn't take place.
What's wrong with that? Where should the pic uploaded from "image/flash" display?
Is it possible that the issue is common, due to I'm still in a 7-day free trial? I'm really confused...