Image viewer for renaming the current image

Solution 1:

Geeqie Image Viewer will do this.

http://geeqie.sourceforge.net/

apt-get install geeqie

or

http://sourcedigit.com/19324-19324/

Solution 2:

XnView Multi Platform will let you rename images "on the fly". Simply click on the file name in the thumbnail view and change the name.

https://www.xnview.com/en/xnviewmp/