Obviously. But with this special type of people-watching, you can determine which country your line-mates are from by peering at their passport covers or where they are coming back from, judging by the souvenirs they are carrying or the clothes they are wearing. You can also make-up "storylines" for these travelers such as "Honeymooners." "Cruisers." "First vacation together." "Retired folks." etc. Of course, your observations will probably be far from the truth. We once crafted a love story between two travelers, only to discover when it was their time to approach the customs desk, that they weren't even traveling together.
Talk to Your Line-Mates.
Instead of making up stories for your fellow travelers, you could, you know, talk to them and find out where they're from and where they're coming from. This is actually helpful when you first land in a new country as they may have some good tips to give you about how to get around and what to do.
Read a Book.
This is especially useful if the line is not moving very fast. But it should be a pocket-sized book that you can easily hold with one-hand while you pull your carry-on along. Also, a magazine or newspaper works pretty well here too.
Notice another single traveler in the line? Why not hit them up and see if a love connection can be made. It's clear you two already have international travel in common.
Fill Out Your Customs Forms.
If you forgot to fill this out while on the plane, now's a good time to do it. Just make sure you have a pen handy.
Got another way for killing time while in the customs line? Share it in comments below!
[Photo of the immigration line at London-Heathrow: Jaunted]