While you could create one for personal use, it's important to note that abbreviations are usually used for:
* Long and frequently used words or phrases: For example, "Mr." for "Mister" or "etc." for "et cetera."
* Technical terms: Like "DNA" for "deoxyribonucleic acid."
"Imagination" is a relatively short word and isn't used frequently enough in a formal context to warrant a standard abbreviation.