Make sure you're on the Finder menu and click system preferences, then go into keyboard and mouse, and click on the mouse button. for the right button allocate it to secondary button, and this should do the trick. then you will be able to right click on images with your mouse in safari, and select download linked file as. etc etc. Good luck!
oh by the way, you didn't specify if you're using an external mouse or the trackpad on your laptop, if you're using your laptop then holding down the CTRL button while you click will bring up the right click menu options also. this will also work on an external mouse.