I think motif is the right word I need for this. I have been thinking of starting a fairly large project to do bit by bit and was wanting some advice on the actual method to do it. I want to make a blanket out of knitted squares but on each square I want to try and knit different images like a heart on one, a teddy bear on another etc. How would I go about doing this?
First, do you want to do colorwork or are you more interested in texture patterns which could be done in a combination of stockinette and garter stitch or reverse stockinette? There are sampler patterns for afghans that use different stitch patterns for the blocks. Have you tried searching at www.ravelry.com? You might find something you like there.
many people use the washcloth patterns, and also the various blanket square pataterns. just have to figure out which images you like, and size them accordingly.
http://www.knittinghelp.com/free-patterns/categories/dishclothes-potholders and a search for ‘blanket square’ on ravelry would be great places to start. 
I was looking to try colour work on the squares but I do not know how you would change between the different colour yarns when needed etc. Finding patterns to follow I would have no problem with now thanks to your suggestions but it is more the theory of how to do it I would like some extra advice on.
If it’s fairly large areas of color you could do the intarsia technique.
With smaller areas of color or more detail, a stranded technique may work better.
Thank you very much! That makes so much sense!