Press the Print Screen/SysRq button on your keyboard, then get a program like Irfanview to resize the image and/or turn it into a *.jpeg* file. Then get an account at Photobucket and upload your pics there. Then in your post copy in the IMG code and you're done.
While this thread is here... Is there a quick fix for alpha on ground textures turning black in the images, or is it just some textures that are affected? Should I test every texture with a screenshot? TRS06 with Irfanview.