As you can now make screenshots with steam e.g. press "F12" you just have to upload them per one click and set visibility.
When you want post them here just make fullsize of picture and rightclick, then choose "sourcecode"....on the bottom of the rollout, copy the lne you see in new text window.
Put the full line in your post and just add width="800" height="600" at the end of the adress....it looks like this at the end, you can also choose different siz ratio.
...zwhjewjhehjw.jpg" width="800" height="600" />
I think this is the fastest and easiest way to link them.
HF