In the module i can set to use an iconset.
Instead of the option to choose colored or white_grey it shows a path to the icons.
If you select one and you will not see the icon.
In Firefox i can see "<img src="http://toeere.allesoverkerkrade.nl/modules/mod_joomleague_matches/assets/images/home/deb93323/domains/allesoverkerkrade.nl/public_html/toeere/modules/mod_joomleague_matches/assets/images/white_grey/date.png" alt="Datum" title="Datum" width="16" height="16">
I don't know were to change this