Step 1: Go to http://imagevenue.com/
Step 2 Once your at the site you will see 5 'Browse' Buttons. Click browse and select the image(s) from you computer that you want to upload. Then Select if the content is safe or unsafe for work (if it contains nudity select not safe) and hit the send file(s) button. Refer to below screen shot for a example.
Step 3: After a wait, how long depends on how many images you have uploaded and how big the file size it, just be patient and wait for the next page to load, which will look the the screen shot below.
Step 4: Now once you want to copy the Hotlink clickable thumbnails on a Forum or Message Board codes, its the top box. Refer to the screen shot below for example.
Step 5: Now just copy and paste that code into your post and thats it. It is always a good Idea to preview your thread first just to make sure that everything has went ok.
Here is the final result.
