Well now you can. Install the extension and visit it's options page for more details about how it works!
chrome-extension://lhlckkgdiojkapplglfeomlkjllphilo/about.html
Note - you have to manually allow access to file URLs once the extension is installed, similar to how you might allow extensions in incognito mode.
Enjoy!
Fullscreen Slideshow Steps:
1) From options set body CSS to background-color:black;
2) Consider checking the option to reduce flicker if URL bar matters not
3) On windows press F11 to enter fullscreen, on mac press Command+Shift+F
( note: version 0.19 contains a bug where the save button will seem to save formats other than PNG. It does not - all files saved with this version are PNGs. Version 0.20 will save JPGs in addition to PNGs. )