There is no VM image, an image (operating system) is what your referring to ie OpenATV5.1
Then you have skins that can be loaded or downloaded from the plugin menu on to your receiver to make the it look like the real thing.
popular images are Openvix (great for first timers as softcams, autoboquets are preloaded)
OpenATV (theres a little more work to do setting this one up)
Then you have pre-built images that forum member's have set up and saved allowing you to download.
My advice would be to spend a few days reading some threads on here to familiarise yourself with the different images/skin set up etc.
You will get plenty of help on this forum, some very helful fiendly people on here:)
Have a look here at Kidda C's VM look a like skin
http://www.techkings.org/zgemma-star-2s/94048-new-skin-vskin-hd.html
Edit: The model of receiver that you have purchased is a twin tuner for sat only, if you have a VM feed then you would best using a cable receiver to get the full HD package as sly is only in SD now.