The image in question is located in a ControlTemplate inside of a ResourceDictionary similar to this (various details removed for clarity):
<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006">
<ControlTemplate x:Key="ImageTestTemplate" TargetType="ImageTest">
<Grid>
<Image Source="/MyAssembly;Component/Images/MyImage.png"/>
</Grid>
</ControlTemplate>
</ResourceDictionary>
When I view the control in Expression Blend the image shows up just fine, but when I run the app the image does not show up. If I drop the same image into a UserControl it also shows up just fine, so the problem has something to do with using the template.
Is there some other way I should be loading the image resource inside the template?