What do you mean exactly? If your sending art to others you could just email it. However if its for custom images or images on the forum etc for others to view you can use picture hosting sites such as photobucket.com etc and then post the links.
Click the number of CPs you have, and then choose the Exchange CPs link at the top of that page.
Somewhere on that new page will be a series of text boxes where you can choose what sort of entity you want an image for (ship, item, room, etc), and then you type in the ID number (found from the inventory pages), and the links for the large and small images. Click submit and the art team will have a look at them and either accept or reject them.