The Stone's global works fine - with two small corrections to the calling routine: <%name%< instead of <%Name%> and with a final <%endloop%> (<%endif%> generates an missing endif error)

Therefore:
<%view_checked('Pictures', $Pictures)%>
<%loop loop_Pictures%>
<input type="checkbox" name="Pictures" value="<%value%>" <%if checked%>checked<%endif%>><%name%><br>
<%endloop%>

Thanks indeed TheStone!!