I was trying to upload a webp image on an image hosting site and implement it here but I failed. [...] Is it a problem from image hosting site or from bitcointalk?
Well, based on pure logic, since you could not upload your .webp image on the image hosting site, what's the connection with the forum?

It's a problem that the respective image hosting site does not let you upload .webp images.
I tried with 2 different sites and still, the result was the same.
This should have explained you already that there is no connection between the forum and the sites where you tried to upload your image...
So, I took a screenshot and used that image, and finally, that worked.
Yes, that worked, because the screenshot was saved as .jpg or .png and the image hosting site was accepting this type.
What was wrong with my initial webp file?
There was nothing wrong. It's just the image hosting site did not accept this format. I tried to upload a .webp image on imgur and it doesn't work. This is what it shows:

As far as I know, according to theymos, only forum limitation regarding images is the one about their size:
1.5 does really suck, 2.5 would be perfect
OK, I increased it to 2.5.
If you have any other complains, well...
