In the gallery you'll be able to see, share, and download your friend's drawings. In order to do so, you must access the "Friends" tab.
There, you'll find a list of all your friends and you will be able to access their drawing history by tapping on their profile picture. In the upper right corner of every drawing you'll have the option to download/share it.
In the Gallery section, you'll see both yours and your friends' drawings.
You can follow new users in order to see their drawings in the gallery. To do so, you must enter the chat, start a new conversation, and tap on "Follow", located in the upper right corner of the menu.
In order to make sure you can see the drawings, exit and reenter the game.