Using memcached to host images
Yes, you can do it.

Create a controller or serlvet called for example
www.yoursite.com/getImage/ID
When you execute this URL, your
program shoud connect to the memcached and return the image object
that you have previously stored in it. 
Finally when in your html you add: src="www.yoursite.com/getImage/ID" the browser will execute
this url, but instead of reading a file from disk it will ask the memcached for the specific ID.

Be sure to add the correct content-type in your response from the server in order that the browser understand that you are sending an image content.
Fer
Im writing simple blogging platform in Flask microframework, and I'd like to allow users to change image on the front page but without actually writing it into filesystem. Is it possible to point src attribute in img tag to an object stored in memory?