You may try something like that :
<asp:Repeater ID="rptEntries" runat="server" DataSourceID="dsEntries">
<ItemTemplate>
<%# String.Format("<div class=\"imgThumb draggable\" style=\"background-image:url('uploads/{0}');{1}\" data-id=\"{2}\"></div>"
,Eval("entryImagename")
,(Convert.ToInt16(Eval("entryWinner")) == 1)?"":" filter: grayscale(100%);",Eval("pk_entryId"))%>
</ItemTemplate>
</asp:Repeater>