In Salesforce formula field using IMAGE(image_url, alternate_text, height, width) function, we can insert an image with alternate text and height/width specifications.

In below example, I’ve created a custom field “Priority__c” in “Case” object with below formula. This formula displays a red, yellow, or green flag image to indicate case priority High, Medium or Low.

Formula Field:

	 
IF(TEXT(Priority) = 'High', IMAGE("/img/samples/color_red.gif", "Red", 10 , 50), 
IF(TEXT(Priority) = 'Medium', IMAGE("/img/samples/color_yellow.gif", "Yellow", 10, 50), 
IF(TEXT(Priority) = 'Low', IMAGE("/img/samples/color_green.gif", "Green", 10, 50), 
NULL)))

Output: