This should have explained you already that there is no connection between the forum and the sites where you tried to upload your image...
I think I had bad choices of word. I was able to upload the file on image hosting site without any issue, it allowed me to upload webp file if I'm not mistaken but when I implemented the bbcode on bitcointalk, the image wasn't displayed here.
As far as I know, the forum's image proxy is limited to GIF, PNG and JPG (probably also JPEG).
I see. I have used gif, png and jpg. Can't remember if I have ever used JPEG or not.