OpenTTD (0.7.2) does install icons and man-page in directories just specified for configure with --icon-theme-dir and --man-dir. Both settings miss one level of directories. So instead of there being (only relevant parts shown) ./configure \ --icon-theme-dir=/usr/share/icons \ --man-dir=/usr/share/man there should be ./configure \ --icon-theme-dir=/usr/share/icons/hicolor \ --man-dir=/usr/share/man/man6 That way icons are where all others are and man-page (openttd.6.gz) gets installed to group 6 instead of man root.
this is fixed in 0.7.3. Thanks for the bug report.