You can but you don't have to use a photo hosting source to post pictures on our forum. I don't bother with them any more now that the Forum's software has been updated.
If your on the forum with a system that can "Copy" and "Paste" and you can open the picture, you can Copy and Paste it into your post on the forum as long as it isn't too large.
You can also use the blue "Upload a File" button and navagate to the picture and then "Open" it.
Follow this link to find out how to post a picture on the forum. Also, read the second post in the link to learn a method of reducing the file size of the picture. Doing this can allow you to post many pictures in your post without going over the file size limit.
https://www.muzzleloadingforum.com/threads/posting-a-picture-on-the-forum.115183/