I agree with most of what you are saying here. IMHO we just have to wait to see what the planned theme actually is. Right now all we have is a name, a location and one very vague piece of art. If the rest of the resort turns out to be plain and un-themed I will be the first to step up and call them out on it. The theme doesn't have to begin and end with the room towers. A lot more goes into it. I will throw out the Royal Pacific Resort at Universal as an example. IMHO its a very well done resort with a pretty good overall theme. Some people argue it out Polynesians the Polynesian. I'll table that debate for another thread. My point is the actual towers with the rooms are not all that impressive. Here's a picture:
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Where the resort's theme really takes off is when they add in a really nice tropical looking pool area:
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Some elaborate themed fountains:
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And various Polynesian themed elements in the lobby and common areas...
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...and you have a pretty well themed resort which rivals most on Disney's property.
My point in posting this is if you just looked at the first picture showing the plain yellow hotel tower and tried to judge the quality of the theme of that resort you would most likely come up with the conclusion that it's not well themed and that's far from the truth.
I am a realist so I have no delusions that Riviera will rival Royal Pacific but that doesn't mean it won't have a cohesive theme either. As I said before we have to wait to see more before judging the whole thing.