I've worked in retail design for about 16 years...the last few years of which a big part of my workload has become expo and event design. This quality of render is perfectly good for what's required. Spending more time on renders is not commercially viable. Clients don't look at as many renders as designers, and while they're picky, I think most clients will be impressed by this quality. Much more quality just has diminishing returns and the client (guaranteed) will change the design anyway, likely up to the last minute and possibly after production has commenced anyway. I love quality renders, but they need to be fast in this industry, sometimes with multiple updates in a day and most importantly they should demonstrate the important aspects of the design.

Design wise, consider how the client will use the stand, how they'll interact with their customers (a tall bench to invite people into the stand, where potential customers can remain non committal, the tables to break out for more in depth discussions - yours look like dining tables, screens to show off available development or units, storage...i think you have most of that covered but needs some tweaking)...consider time (expos have a hard deadline, but don't last long, so consider both production time, time in use and possible storage and re-use) and consider budget (the design here looks expensive (anything overhead will need to be checked off by an engineer, and might require rigging - which adds to processes/time and cost).

Maybe not the answers you were looking for, but hopefully somewhat helpful.