You need to talk to your target user group but I just did some searches for antique unusual or bespoke bed tray tables and was surprised that there weren’t any particularly interesting or unique examples to get inspiration from. Would have expected some industrial revolution inventiveness or some handmade bespoke for rich ww1 injured officers. That tells me there isn’t a way for a bed table to make life much easier for those confined. But doesn’t mean you can’t use better materials, antibacterial or lightweight etc. For example this bamboo table is great being lightweight with cup and side holders but is labour intensive to make and not easily cleaned so maybe get examples like this showing the pros and cons and show where you improve the cons? And of course since you are a design student make sure it’s more aesthetically pleasing than the current offerings.

My wifes's dad was disabled, initially because he only had one leg and many years after that from a stroke causing total left side paralysis. The easiest ones to use are like the ones in hospital, they can be pulled over the bed as they are on wheels, the height is adjustable, they offer a lot of working / eating space and can easily be pushed back with one hand when not wanted. The lap trays are ok, but they require someone else to come along and remove them. Have a quick look at the ones you can buy in Argos, had a quick look and they do 13 different ones.

I think when designing something like this, it has to be easy for the disabled person to operate themselves, as it's really frustrating for them having to have help all the time.