a viewer to display inserted images into posts that are hosted elsewhere

I am using Network theme and have about 50 subsites.

My site reviews games, etc. and in each post I would like to insert screenshots that are hosted elsewhere (so by URL) of the games I am reviewing. So, I need a small image slider that will display the screenshots nicely, with previous, next on top or somewhere, into each post. I don't want to use nextgen gallery as it has too many extra features...any idea on how to do this nicely/cleanly/easily? Also, I do not want the featured image of the post to show up in there, so I would have to exclude it.

Any suggestions would be highly appreciated!