Flash - SWF
Flash files are sometimes wrapped in EXE files. File Juicer can extract most of them by removing the Windows code, so you can play them on macOS too.
File Juicer can extract JPEG, PNG and GIF from SWF. Flash can use alpha channels on JPEG images, but this is not a feature of JPEG files and this is therefore not extracted.
You can play SWF files without a web browser if you download iSwiff. Where I have also collected a few links to Flash game sites.
Flash Video - FLV files are not stored in Safari's or FireFox's cache but in Mac OS'x Temporary Items folder which you can search form File Juicer's File Menu.