One way to make a room appear more roomy/larger is to have the walls, flooring and most of the furnishings be in the same color family.
Lets say the wardrobe is a light color wood or paint...painting the walls the same or very similar color will make the wardrobe blend and the room appear larger.
Now if the flooring is also a light tan/beige for instance, the whole room will appear even more roomy.
If the flooring is dark and the walls and wardrobe is light then get a large area rug in a light color or pattern to continue the light color theme.
You can then use light color bedding and curtains. They do not have to be tan/beige but can be a light color that you like.
Limiting the clutter will also help to make the room appear and feel larger.
Now, if the wardrobe happens to be a dark wood or paint, find a similar paint color for the walls only a couple of shades lighter. Same for the floor/area rug.
The bedding and curtains could then be a shade or two lighter than the walls, you could even use prints, basically using the same color family throughout the room in different shades and textures.
If you cannot paint the walls, then maybe paint the wardrobe to blend with the walls.
Better lighting also helps.