You can for example upload your pictures there : http://imageshack.us/ . When the file is uploaded, ImageShack gives you several codes. Then you copy/paste the first "forum code" in the message box of Insecterra.
Example of Forum code : [URL=http: https://2img.net/r/ihimizer/i/stenoriapl.jpg/][/URL]Uploaded with [URL=http ://imageshack.us]ImageShack.us[/URL]