Ok, the On_After_Change is solved , because the value was not being set.
Binding I was able to do with modifying the view.xsl, and changing the following:
xd:binding="xdXDocument:GetDOM("mycon")/myfield">
<xsl:attribute name="src">
<xsl:value-of select="xdImage:getImageUrl(xdXDocument:GetDOM("mycon")/myfield)"/>
</xsl:attribute>
But I am wondering how I can make a property page for this contorl that shows up in the infopath together with the rest of the property pages..Because, it is a big hastle to keep changing the view.xsl each time.