What are all these large files and can I get rid of any of them?
Obviously you have or had an Android SDK installed. These images in the SDK are used to test different android versions on the emulator. Simply right-click one of the file and choose "Show Enclosing Folder" and you will see to where they belong or what they exactly are.

If the Android SDK is still installed, you should be able to deal with them using the SDK Manager.