I completely agree about getting in closer to the barn. Or, if the barn is surrounded by a nice landscape (strong lines or colours, not too cluttered), you could even choose to back up and incorporate it into its surrounding a little more. About the photo being dull, I think it's because it's a bit overexposed, which washes out the colour. As long as the overexposed parts still have detail, it's an easy fix in PhotoShop. :)
The first thing I thought was that the lighting is very harsh - I totally agree with Steve. Perhaps even an overcast day would help get rid of the extreme contrast and allow you to get more middle tone detail in the wood of the structure. I like the idea of getting in closer to shoot more details of the barn, I see some really good potential for abstracts with all those crazy lines. What bugs me in the composition is that the barn is dead center horizon, I'd come in closer and put the barn in the bottom or top 1/3 of the frame. I think maybe some slide film with good saturation (velvia 50) would help make the colors pop a bit more, especially if you get dawn or dusk lighting.
OK, looking at this photo, I try to visualize the different angles from where you might have shot it to improve the image. First, the light is fairly harsh. If there is nice light at dawn or dusk at this location (it might be blocked by the trees) that may help. If there is any element in the foreground that could lead the eye into the image (a fence, a cow, etc) that would help. The solid darkness of the trees brings the barn out from the background, but adds little interest overall. The character of the barn and the way it leans in several directions is interesting, but by itself, the image doesn't quite make it, as you realized. You may also consider shooting some details of various parts of the barn. The roof line, if you shot just the top of the roof could make a fun photo. Experiment with different focal lengths to get different perspectives. And one further suggestion, use a tripod and get that aperture much smaller. F5.6 isn't enough to get maximum depth of field for a landscape photo.
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