Dynamic images

 I have to insert a dynamic image (those images will be located in the server) in my rtf template. My report gives some information about diferents cities and when I select a city it should appear an mage of this city.

I've been doing some tests to get it.

First, I've inserted a dummy image and in the alternative text I've written the url of an image I've found in internet. The result is that this images only appears in html format, but not in pdf or rtf. How can I solve this problem?

Another question is about the location of the images in the server. Must I keep the images in a specific directory of the server to use them?