The icons are only defined on the OVFIndex (it was hardcoded there) but the OVF envelope document have no reference to the icon, to set it can do the follow:
on the top level virtual system, get its product section (these informations is used on OVFIndex) and set the fileRef attribute of the icon element as:
option1) the full path : fileRef="
http://abispace.s3.amazonaws.com/ubuntu-9.04/ubuntu_logo.png"
option2) a package relative path : fileRef="icon" and then define a new File on the references section with the same id ("icon") and with attribute hRef="ubuntu_logo.png" (assuming these file is on the same package folder)
the option2 is more standard compliant.
Improvement
Open
Minor
Any of the OVF packages on the public RemoteRepositorie (abispace on s3) have the icon properly set
<ProductSection>
<Info>mw</Info>
<Product>mw</Product>
<Vendor>mw</Vendor>
<Version>5.0</Version>
<ProductUrl>http://www.abiquo.com/</ProductUrl>
<Icon ovf:mimeType="image/jpeg" ovf:fileRef="icon"/>
</ProductSection>
and the reference section as :
<References>
<File ovf:id="image_mw" ovf:href="AbiquoMW.vdi" ovf:size="111150592"/>
<File ovf:id="icon" ovf:href="icon.png" ovf:size="5646"/>
</References>
the file 'icon.png' should be on the same folder as the OVF description