The forum will supoort a variety of embedded content.
If you want to embed a 3D model you can use SketchFab. Simply create an account and upload your 3D work, then paste the full URL to it into the forum and it will automatically display it and allow users to zoom in and out, turn the model 360 degrees etc.
You can also paste images directly into your post feom your clipboard, or drag them into your post as a file.
If you want users to download a file the maximum size is 10mb, for content/projects larger than that you can link to Google Drive or DropBox for example.