Sib Icon Editor is described as 'Icon editor for Windows. Sib Icon Editor is an easy-to-use icon manager, extractor and creator. It allows to make web buttons, favicons and icons for mobile devices' and is an app in the Photos & Graphics category. There are four alternatives to Sib Icon Editor for Windows, Mac, Linux and Windows S. The best alternative is IcoFX. It's not free, so if you're looking for a free alternative, you could try JDraw. Other great apps like Sib Icon Editor are Icon Slate (Paid) and icoworks (Paid).
JDraw is a pixel oriented graphics editor designed especially for small to medium-sized pictures used to decorate web pages. It is completely written in Java, simple to use and saves (animated) GIFs, ICOs and PNGs.