Short story
On Slackware 14.0 I could run icewm 1.3.7 well. It needed only to recompile properly gdk_pixbuf to show icons.
Compiling icewm 1.3.8 was so tough that I upgraded to Slackware 14.1. But icewm on Slack 14.1 is broken, see attachment.
Long story
There are a lot of reports about this issue on Internet; so on Slack 14.1 I compiled new gdk-pixbuf-2.31.0.tar.xz (needed also glib-2.40.0.tar.xz, libffi-3.1.tar.gz, Python-2.7.8.tar.xz) but the issue remains.
Both icewm 1.3.7 and 1.3.8 has trouble on Slackware 14.1. Moreover 1.3.7 does not show icon in left-top corner of window.
Have to say that included themes works as expected. The troubled themes are collected from Internet (IceSimple, IceClearLooks2, IceTunes).