Pixel Studio (FileStream)
From Just Solve the File Format Problem
Pixel Studio is a bitmapped graphics editor for Windows. It was developed by FileStream, Inc. Its main native file format is its IBW (Pixel Studio Work) graphics format.
A possible signature is that IBW files start with bytes
0x2c 0x2d 0x00 0x00.
- Pixel Studio 2.0 - CDROM image at Internet Archive