The technique you're referring to is called intarsia. Yes, the back is not 'finished' the way the front is.
You can use duplicate stitch, basically sewing over the knit stitches with a different color, to put a picture on knitting if you don't want it to show on the other side the way intarsia does.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry