In SketchUp do "File -> Export -> 2D Graphic", save the .png file somewhere, then upload the saved file to the TP forums by clicking on the "Choose File" button, pointing to the saved file, click "Add the file" and then clicking on "Place inline". If I do all this I get this:
Attachment:
File comment: TEST
TEST.png [ 34.47 KiB | Viewed 1055 times ]