Moreso not the LINKS you are looking for.


Given the above works (I shrunk the images first)
from what I can tell you are linking to pages with the image not the image itself.
With dropbox you need the public link for the image itself so it needs to be stored in your public folder. The link itself will be much like this; dl.dropbox<whatEverElse>/<filename>
This can be done with drop box running on your computer by right clicking the file in the dropbox public folder and choosing get public link. and using said link in your image tags.
The web browser interface also has the ability to copy the public link by right clicking on the file itself as well.