Depending on what they're selling, advertisers are usually pretty good at selecting photographs that match the product they're pushing. Selling an iron? Here's a picture of an iron. Promoting a concert? Here's a picture of the band. Trying to get you to meet girls in your area? Here's a picture of an under-aged teen we stole from Google.
Trying to get people to enroll in an online college? Um...well...all I have is this picture of an angry old dude. Good luck.