I love this colorful world! Here are some tips to fill it with life:
You mentioned you might want to include a little background story in there, so I’d recommend you to use environmental storytelling. Include details that hint at the background story by raising and answering questions (why isn’t there anyone? Who are the people who lived there? What’s the history of the environment? For what purpose did this very structure exist? What are the jobs and activities of the inhabitants?). Don’t make your hints to obscure, though.
Try this on your current scene: In the back, there seems to be a solid building - it looks like it took some time to build it, so is it for permanent settlement? In contrast to this, why is the shelter in the foreground so tiny and simple? It seems there was another building before, but it vanished. The fence seems to enclose a small area - was it used to farm animals (In this case, you could add animal footprints in this area)? Where does the path lead to? If the path is short, you could make it look heavily used; if the path is long, there might be a signpost.
You can build your world out of your story, even if it’s just a single event - just imagine what the world would look like after. If want to get help on building the setting of your world, you could head over to the Worldbuilding Stackexchange, an extremely useful website.
If you can deliver an interesting story, the user’s experience will be much more immersive. The story doesn’t have to be complex - even if it’s just as simple as “a volcano erupted and everyone died”, it will interest the player.
One thing you might want to think about is: Is the player “really” there, like he woke up and everyone vanished, or is he an observer?
Another interesting storytelling alternative is to use a narrator that comments on specific aspects the player does, explores, etc. (you can take Rucks from Bastion as an example).