Check out this (very) old thread...
http://forum.kodi.tv/showthread.php?tid=152716
and here is another example, using the ACE skin...
https://www.youtube.com/watch?v=dJ4Smsd2DUY
Also, I read this (seems easy enough)...
Viewing CBR's and Pics
One of the things XBMC is capable of is viewing your photos of all types including RAR ,CBR, CBZ ,and many other forms of compressed files.
You can make your own .cbr file by putting some of your photos in a folder compress them and rename the rar from "photo.rar" to "photo.cbr"
Comics and picture navigation are the same.
0-9 number keys will zoom
left and right arrows will go to next and previous while in default view
if you have zoom engaged press "comma" and "period" keys to go to next and previous page or photo.
Supported picture/image formats:
CBR/CBZ comic books (RAR/ZIP archives renamed)
BMP picture/image
JPG/JPEG picture/image
GIF picture/image
ICO picture/image
PCX picture/image
PNG picture/image
RAW picture/image
TIF/TIFF picture/image
TGA picture/image