1. Alpha channel for layering purposes.
2. A square not weird rectangles.
3. 2500X2500px previously 600dpi was a liiiittle too much. I think there is no need for a larger set anyway. 2500^2 should serve well.
Made with FilterForge2! 30,000 variations are available I'm developing it as a filter. If you are a user of FilterForge 2 you'll be able to use it to make your own customized zoomlines. It may take a while, I am slightly busy making other things.
and lastly the deviation with download link: