First of all, I moved your post to
Shotgun category as it’s more related to web UI.
To answer your question here, unfortunately there is no way to scale the icons to be larger than 16x16. It has to been an 16x16 PNG/JPG file (GIF works too, but PNG/JPG is preferred), and yes the icons are centered in the cell.
Disabled Statuses are the only ones that were engineered into the UI at it’s conception and are not updatable on the client side. Unfortunately, it’s not something that is simply accomplished by us either, as it involves altering the underlying database tables. New Statuses only have the pictorial representation of an icon via the 16 x 16 PNG.
We have logged a feature request for the ability to have text as an icon, but feel free to submit your idea via our Roadmap Portal