Currently, supported texture formats are .png, .jpg, and .bmp.
Just set Importer name to TextureImporter and Processor name to TextureProcessor, like below.
<Item Include="\Textures\Impression.png">
<Name>Impression</Name>
<BuildAction>Compile</BuildAction>
<Importer Name="TextureImporter" />
<Processor Name="TextureProcessor">
<TextureFormat>Compressed</TextureFormat>
</Processor>
</Item>
Defaultly, TextureFormat is Color and to get best performance when rendering should be set to Compressed. You can create custom Importer library .dll to support other texture format.