I found all of the following resources as free downloads on the Internet. However, usage guidelines vary: for example, some artists require that you credit them when using their work. Please check each individual download page for usage guides.

Suitcases
These six suitcases come in funky colors, angles, and rotations.

Vector Travel Icons
To use these two sets of travel icons, you can either open them as JPGs in Photoshop, or you can try the vector EPS versions that you can modify in Illustrator or place as smart objects in Photoshop.

Planes
This airplane brush set is useful in many situations.

Concept Cars
For travel with a futuristic edge, the Concept Car Brushes by zoomanchoo is ideal. There are 14 vehicles in all.

Old Cars/Bike Brushes
Are the concept cars too cold for you? Try these vintage car illustration brushes.

Vintage Correspondence
I'll round out this travel series with more vintage-look Photoshop brushes. First, here are 15 stamp brushes:

And lastly, here is a postage label brush set.