The AWStats package in RHEL4/Centos4 and Plesk 8.1 uses an alias directory for the icons called /awstats-icon, but when the AWStats contents is generated, the icon directory is different (/icon). To fix this issue, change this file:
/usr/share/awstats/awstats_buildstaticpages.pl
my $DirIcons='/awstats-icon';

Known bug in plesk, their solution is to edit configs:
http://kb.swsoft.com/article_49_1743_en.html
None of the icons are shown up on the AwStats stats pages.
Article ID : 1743
Last Review : Mar,15 2007
RESOLUTION
This problem fixed in Plesk 8.1.1 Until Plesk 8.1.1 release you can modify AwStats configuration files with:
sed -i 's,^DirIcons=.*,DirIcons=\"/awstats-icon\",' /etc/awstats/*.conf /usr/local/psa/etc/awstats/*.conf
After next statistics utility execution by cron the icons will be shown up correctly.