i can't put photos in topics

[Tetri the Yumemi Fan]

i wanted to post new episode i made but i struggle with sending pictures to the topic, can someone tell me how to fix it?
it says "System error: result type not supported"

[deice]

you might be trying to upload an image that's in an invalid format
while the file dialog does present a wide variety of formats, in my experience not all of these are actually supported by postimg, so it's best to stick with something like jpg or png

(also keep in mind that this is not something smbx forum administrators have direct control over, postimg is a third-party service)