Meh, finished my half-written-out thought in a FIXME in Special:Log code.
.mceItemFlash, .mceItemShockWave, .mceItemQuickTime, .mceItemWindowsMedia, .mceItemRealMedia {border:1px dotted #cc0000; background-position:center; background-repeat:no-repeat; background-color:#ffffcc;}
.mceItemShockWave {background-image: url(../img/shockwave.gif);}
.mceItemFlash {background-image:url(../img/flash.gif);}
.mceItemQuickTime {background-image:url(../img/quicktime.gif);}
.mceItemWindowsMedia {background-image:url(../img/windowsmedia.gif);}
.mceItemRealMedia {background-image:url(../img/realmedia.gif);}