If you get the feeling that you photographed everything, or lack imagination when stock-working just do the following:

- make a list of your favourite 10 categories

- pick one of the categories randomly and draw/photograph something on that subject

- next day you pick another subject...

..and now a little exercise of creativity... (sometimes its hard to photo something from that special category you just picked):

- open any book and put your finger on the surface of any page at random.... look.. it will be a word you picked.. try to combine that word with the specific cathegory.

Here's an example:

Suppose you have the "business-metaphor" cathegory and you take a book and accidentally place your finger on the word "heart". Then you get the idea of drawing a heart exploding with money ( lol... i just made that out.. it's fresh ).. or any other idea.

Working like this you'll see an increase in creativity.. you'll become more imaginative.. there will be more ideas, concepts and your work will become more ingenious..