Skuid Page XML for logging a Case from a Force.com Site and pre-creating a skuid__Image__c record that gets thrown into a "skuid__Photo__c" field on the new Case.

LogACaseWeb.xml

<skuidpage showsidebar="true" showheader="true" tabtooverride="Case">
   <models>
      <model id="CasePhoto" limit="1" query="false" createrowifnonefound="true" sobject="skuid__Image__c">
         <fields/>
         <conditions/>
      </model>
      <model id="Case" limit="1" query="false" createrowifnonefound="true" sobject="Case">
         <fields>
            <field id="Subject"/>
            <field id="Description"/>
         </fields>
         <conditions>
            <condition type="modelmerge" value="" field="skuid__Photo__c" operator="=" model="CasePhoto" enclosevalueinquotes="true" mergefield="Id" novaluebehavior="noquery"/>
         </conditions>
      </model>
   </models>
   <components>
      <pagetitle model="CasePhoto">
         <maintitle>New {{$Model.Case.label}}</maintitle>
         <subtitle>{{$Model.Case.labelPlural}}</subtitle>
         <actions>
            <action type="savecancel" afterCancel="/products" afterSave="/apex/skuid__UI?page=ViewCaseWeb&amp;id={{$Model.Case.data.0.Id}}" window="self">
               <models>
                  <model>Case</model>
               </models>
            </action>
         </actions>
      </pagetitle>
      <basicfieldeditor showsavecancel="false" showheader="true" model="Case" mode="edit">
         <columns>
            <column width="50%">
               <sections>
                  <section title="Basics">
                     <fields>
                        <field id="Subject"/>
                        <field id="Description"/>
                     </fields>
                  </section>
               </sections>
            </column>
            <column width="50%">
               <sections>
                  <section title="Additional Info">
                     <fields/>
                  </section>
               </sections>
            </column>
         </columns>
      </basicfieldeditor>
   </components>
   <resources>
      <labels/>
      <css/>
      <javascript/>
   </resources>
</skuidpage>