.htaccess is your friend there if you want to prevent deeplinking those images from other sites.
Exampje 1 .htaccess that will deliver broken images to anyone deeplinking to it:
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^https?://(www\.)?themepark.nl/.*$ [NC]
RewriteRule \.*$ - [F,NC]v2 replaces any deeplinked image with our "don't steal the bandwith" image.
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://.*themepark.nl/.*$ [NC]
RewriteRule \.(gif|GIF|jpg|JPG)$ dontstealourbandwith.gif [L]