* -ary: "Imaginary" - something existing only in the imagination.
* -ation: "Imagination" - the ability to form mental images or concepts.
* -ative: "Imaginative" - having or showing imagination.
* -er: "Imaginer" - (less common) someone who imagines.
You could also use prefixes to create words like:
* re-imagine: To imagine something again, in a new way.
Remember, the best choice depends on the specific meaning you want to convey.