Hey Richard, thanks for the post.
Both the free and Pro versions of MarkdownPad allow insertion of existing images from somewhere on the web, but Pro offers a built-in uploader that can upload your image to Imgur, a popular image-hosting service. This lets you take an image from your local computer, and automatically have it inserted in your Markdown document.
In the example shown below, anybody can insert a URL into the Image URL field, and it will be included in your Markdown document.
Pro users, however, can click the Browse and Upload button, select an image from their local computer, and the image will be uploaded to Imgur and a URL to the image will be automatically inserted in the Image URL field.
I've received requests to offer additional image hosting services in addition to Imgur, so in a future release I plan to support other methods like self-hosted (FTP/SFTP) and Amazon S3.
Regarding inserting images in this forum: This forum runs on open-source software called Discourse, and it has a built-in "trust" system for new users; kinda like a reputation system. Here's more information on the trust levels in Discourse: https://meta.discourse.org/t/what-do-user-trust-levels-do/4924?u=voxel_pirate
Basically, by spending a little time on the site, you'll automatically get bumped up to the next trust level which enables more features. I'll see if I can modify when users can post images though, as it seems like that would be helpful.
Hope this helps!
Update: Alright, I've modified the forum settings so new users can upload images.