To clarify my question, here are the updates.
Since I understood that some package were already available in the depot, I used PCLI to run the following commands:
Set-ExecutionPolicy RemoteSigned
Add-PSSnapin VMware.ImageBuilder
Add-EsxSoftwareDepot https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml
New-EsxImageProfile -CloneProfile "ESXi-5.5.0-1331820-standard" -name "ESXi-5.5.0-1331820-Whitebox" -vendor "withNICs"
Add-EsxSoftwarePackage -ImageProfile "ESXi-5.5.0-1331820-Whitebox" -SoftwarePackage "net-sky2"
Add-EsxSoftwarePackage -ImageProfile "ESXi-5.5.0-1331820-Whitebox" -SoftwarePackage "net-s2io"
Export-ESXImageProfile -ImageProfile "ESXi-5.5.0-1331820-Whitebox" -ExportToISO -filepath C:\ESXi-5.5.0-1331820-Whitebox.iso
However, it seems I am still missing the package for my particular network card.
Do you know which argument I should add after -SoftwarePackage in the following line and before exporting it?
Add-EsxSoftwarePackage -ImageProfile "ESXi-5.5.0-1331820-Whitebox" -SoftwarePackage "xxxxxx"
Many thanks and regards,
Chris