GridView TemplateField - bind and use App_Themes

Question

I currently have something like this in a GridView:

    <asp:TemplateField HeaderText="Name">
        <ItemTemplate>
            <a href='Link/<%# Eval("Id") %>'>
                <img src="/App_Themes/Default/Images/Icons/<%# Eval("Icon") %>" alt="Icon" />
                <%# Eval("Name") %>
            </a>
        </ItemTemplate>
    </asp:TemplateField>

It works fine, but I don't want to reference App_Themes directly. I know I can create a skin for each image, but I don't know what icon will be used ahead of time. If I have runat="server", I can't use Eval() (designer-generated properties can't be dynamic).

Is there any way to do this only with markup? If not, what's the recommended approach?