Kinma left a good comment here:
Bangalos has a tip here:
I’ve also attached a spreadsheet (CSV file) that lists the origins of the names of the elements. The download link is below the image. That might help with creating images quickly.
You may also want to have a simple number shapes system to memorize numbers.
If you have 50 formulas, you could create 50 locations through your house. Each location could have two places. For example, if one location is your couch, leave space for images on one side of the couch and images on the other side of the couch.
So for this:
I2 + 10HNO3 —> 2HIO3 + 10NO2 + 4H2O
I2 + 10HNO3 could go on the left side of the couch and 2HIO3 + 10NO2 + 4H2O could go on the right.
Also, check out Anki. Even with mnemonic images, it’s still important to review the information. Anki helps space the reviews.
EDIT: the attached CSV file is from Wikipedia and under a Creative Commons license.