Yes, you can specify what text is used for an element (or whatever you want to give a tooltip) using the AccDesc attribute.
Take a look at the style UIFILE for 923, and look for:
code:
usertileview[id=atom(idMainWndUserTile)]
{
AccName:rcstr(46486);
AccDesc:rcstr(44089);
}
The AccName describes the name of it, while the AccDesc is the tooltip. You can change that to:
code:
AccDesc:rcstr(46485);
and it will show something like "Your display picture. Click it to change it." (don't know the exact translation, I'm on a Dutch Messenger version) To look up this number, check "msglang_strings.txt" in the "Strings & Colors" folder of your extractions by Plus! Live. The strings are always preceded by a number, which you can use for anything and you can be assured that it'll work on every Messenger translation.