Dragging and sending pictures to your contact uses the same mechanism than for texts or karma actions. Simply hold a picture for around 1 second and then drag it to the contact of your choice.
You can easily add a new picture by simply clicking on the Add button next to the recommended pictures. Once you have added a new picture, repeat the same process to send it.
You will also see in the main screen a section where you can find additional recommended pictures. Those change automatically throughout the day and week making it convenient and fun to use. The icon for the recommended pictures looks like that: