You can send an image within the Messages page.
Click on the contact/group that you would like to send the message to.
Underneath the text box is a paperclip icon. Click on this to add an image.
You will now be prompted to upload a photo from your phone or take a picture. Follow the appropriate prompts.
Once you select an image or say "Use Photo" on a just-taken picture you will be prompted to name the photo. Once you name the photo it will send automatically to your contact.