Use the password protection in your cpanel. Create user and password for the directory and click the lock directory check box and nobody will be able to go directly into the directory. But yes if you want then to display in your website all you have to do is link to them.
People won't be able to access those images if you protect that directory with a password.
Just think of it this way, if people can view the image in their browser, then they already downloaded your image.
And yes, you can protect a directory with a password in cpanel.
1. Right Click
2. Save Image
Tada! Your image got stolen!
There's almost no way to protect your image unless you copied this website that I know but I forgot the link.
They protect their image with 2 layers. One over each other. The layer ontop is a transparent layer, so when you right click it, you are saving the transparent layer for it.