Anywhere you can enter a Custom Image URL, you can enter items/NAME OF ITEM and that icon will be used.
For example, to use the Snowball Launcher image, you would enter items/Snowball Launcher into the device.
Here is a full list of item names:
Bait
Banana
Beach Fish
Berry Fish
Black Seed
Blackberry
Blue Fish
Blue Key
Blue Keycard
Blue Seed
Blueberry
Bronze Seed
Brown Seed
Cash
Cash Berry
Coffee Bean
Coral Seed
Corn
Cyan Seed
Dark Green Seed
Energy
Energy Bar
Evil Eye
Galaxy Fish
GimBerry
GimFish
Gold Key
Gold Keycard
Gold Seed
Grapes
Gray Fish
Green Fish
Green Key
Green Keycard
Green Pepper
Green Seed
Heavy Shards
Light Shards
Lottery Ticket
Magenta Seed
Med Pack
Medium Shards
Orange
Orange Seed
P.M.L
Pink Seed
Plastic Bottle
Potato
Purple Fish
Purple Key
Purple Keycard
Purple Seed
Quantum Portal
Raspberry
Red Fish
Red Pepper
Red Seed
Research
Shield Can
Silver Seed
Slingshot
Snowball
Snowball Launcher
Starfish
Strawberry
Tan Seed
Teal Seed
Ticket
Water
Watermelon
Wheat
White Seed
Wooden Wand
Yellow Seed
Zapper