How to theme a chunk of content in asp.net site?

I have an ASP.NET site that uses themes to implement a few variations.

I have this user control containing a script and an image.

The requirements are now such that the entire contents of the user control would ideally be part of the theme, but I'm not sure how I can do that.

Am I missing a more obvious solution? (i feel like i might be).

This is the user control - the functionality I'm "conceptually" afer is really like a server side include who's content file gets set as part of the asp.net theme.

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="DirectTrackPixel.ascx.cs"
    Inherits="Controls_Shared_DirectTrackPixel" %>
<script type="text/javascript" src="https://da-tracking.com/lead_third/<%=Pid%>/OPTIONAL_INFORMATION/<%=OptionalInformation%>"></script>
<noscript>
    <img alt="" src="https://da-tracking.com/t开发者_如何学运维rack_lead/<%=Pid%>/OPTIONAL_INFORMATION/<%=OptionalInformation%>" /></noscript>
<asp:Panel ID="ExtraPixelPanel" runat="server">
    <script src="http://hop2.ctrhub2.com/lead_third/1734/OPTIONAL_INFORMATION"></script>
    <noscript>
        <img src="http://hop2.ctrhub2.com/track_lead/1734/OPTIONAL_INFORMATION"></noscript>
</asp:Panel>

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"You can use an @ Register directive in the .skin file. Once the control is registered, skinning works just as you'd expect. "