As you progress through the game and complete various main/side missions you will be rewarded with a host of new outfits. These can be put on by going to your safehouse and walking into the T-Shirt icon.

"Smart Suit"	"Winner"	"Wet Suit"	"Army Fatigues"
"Casuals"	"Leisure"	"Trailer Trash"	"Cuban Style "
"Pastel Suit "	"Tracksuit"	"Hood"	"Hired Muscle "
"Repo-Man"	"Smuggler"