Software for sorting images based on the image data (not file type)
You can use the built in features of OS X to help you narrow down your personal images from system and application images.

AFAIK most Application images and system images are not going to be large. Or wider then either 512 pixels or 1024 pixels.

So I assume all the files are in single folder and your personal ones are taken on a camera or Smart phone so will be of a larger size.

Use Command +F keys to bring up the search options for the open window of the folder.

Set up your search criteria too.

Kind is Image.

And either of the below or a combination.

File size is greater than 300kb

Pixel width is greater than 512

And so on.


There are many more options to use for the search under the other.. menu.
 



You can then move the ones remaining in the results out into a another folder.

Use iPhoto to import the potential personal ones for you final check

Hopefully you will only have a few that are not.