Yeah be aware though, it may be different with your bunny and your special relationship but "trancing" might not always be a fun thing for a rabbit.
I dont want to be overly serious but it may seem be fun for you, but really it should be reserved for serious needs like perhaps examining for wounds etc. I believe this kind of still behaviour is I think a "shock" mechanism for a rabbit, ie playing dead. I might be wrong.
Bunny does look very relaxed in the photo so it may not be as simple as that explanation, but just for those that might draw conclusions and think its great to put every rabbit on its back.
I used to put bunny on its back on the lap more often, but I think you have to be careful especially with their delicate spine as well.
I think we tend to try and keep them upright always, except vicki carries one of ours like a baby as he seems more comfy with her, or if absolutely necessary for things like claws.