D Paint
I don't know about earlier versions, but DeluxePaint II Enhanced for the
IBM PC will read IFF files (up to 8 bitplanes for 256 color mode) and will
also read .PCX files (a format invented by ZSoft for PC Paintbrush, and
used by several other MS/DOS programs). Additionally, EA created a new
LMB format which is not compatible with Amiga .IFF formats and which
optionally includes a shrunk version of the picture for visual browsing.
You can move 4 or 5 bitplane artwork back and forth from the PC to an
Amiga (but you must save your files on the PC in "old" mode in the save
file requestor). Additionally, ASDG's TAD (The Art Department) can convert
new style .LBM files from the PC and 8 bitplane images into regular .IFF
files or even HAM .IFF files. The loader for the new style .LBM format is
an optional extra, but TAD is simply AMAZING, so I recommend it. If you
are careful to save yoour IBM art as "old", you won't need the optional
module for TAD.