When spacefm 0.7.10 is built with configure option --disable-pixmaps (recommended), gtk-update-icon-cache is needed, which is part of the libgtk2.0-bin package (Debian).
The README instructions, manual, provided deb packages, and self-extracting installer have been updated to include this dependency in 0e0a823.
For building a binary deb package, you can replace the debian/control file in the 0.7.10 source with this one.
If building manually without configure option --disable-pixmaps, libgtk2.0-bin is not required.
corrected in 0.7.11