Here’s a boot screen for Windows Neptune I made in April. You can use it by replacing the stock Neptune boot screen in NTOSKRNL.exe with resource hacker. I believe I setup the colour palette so green is the progress bar colour. I’ve had to use a PNG for the preview (It’s a WordPress platform limitation) but the BMP can be found here: http://imgur.com/nkqAc31
UPDATE: I’ve fixed the imgur link to show an updated bitmap which doesn’t show corruption when resource hacked into NTOSKRNL.exe and NTKRNLMP.exe. The original bitmap I shared was a prototype with corruption in it’s rendering due to a broken colour palette.