/Steam/userdata/165471329/760/remote/230290/screenshots/thumbnails/2014-04-12_00001.jpg)
still does not work

You linked to the image on your computer, you need to upload it to the internet and link to the uploaded image.
You could upload it to
http://imgdiode.com/Steam also lets you upload screenshots that you can link to. If you click upload in Steam after taking the screenshot (you can open the interfact by pressing Shift + Tab), then click 'view online' after it's done uploading, click on the image, then copy the URL from the bar in the top of the window.
Paste it here, then put [*img] [*/img] around the link (without the asterisks).
Here you can see the window to copy the link from: