You have to rent space on a computer, host a site, to guarantee pictures will "stay". Big sites like PsychCentral often rent whole computers and run them as well from afar. If PsychCentral goes down for any reason, DocJohn can "fix" the problem himself. I have a site, http://mysharingspaceonline.com/ and my agreement gives me X amount of space. I can upload pictures until I use that space http://mysharingspaceonline.com/angeldevil.jpg. Some other agreements give one X amount of space but also charge per use (kind of like banks charge a check charge if you use more than X checks a month or phones extra for minutes, etc.). That means that whenever anyone clicks on that page/image, they get charged an extra few cents.

People who are charged per use charges, make sure that someone else can't come along and link to their picture and post it another place because, if they post it on their site and you grab it and post it on PsychCentral, all the people who click on and read any post it's in here at PsychCentral will cause a per use charge to that original person who isn't getting any benefit from their picture! So, the red x shows up. Lots of "free" sites do not let you post your pictures and stuff on another site because they're only letting you use their space, not use their space to post elsewhere which costs them "bandwidth" (that's what the multiple use charge is for). That's what "linking back" is. Unless you have rights to a picture, putting that picture somewhere else is using someone else's property and linking back to their site even, can cost the owner or original poster money.