Upload & Sell: Off
Per all reviews and examples I've seen that is a stellar macro lens and also quite nice for other applications such as portraits.
In terms of C&C, when shooting be mindful of distractions in the background around the object. For example in the first shot the green leaf on the ground is a distraction that could have been removed by hand easily. Both shots you posted would benefit from cropping, sharpening, and toning down the background a bit to make the foreground contrast more. Here's the first with about 5 min. of editing.
In terms of lighting, I don't think the lighting here is flat because they are naturally lit from above and are thus what would be seen by eye in person. But if you decide to add flash for your macro work many of the commonly used macro flash strategies do produce flat and unnatural lighting due to the placement of the flashes relative to the subject.
For example ring light flashes like the Canon MR-14 were actually designed originally for medical documentation where flat shadowless lighting was needed inside mouths or body cavities during operations. The horizontally crossed dual flash configuration of the MR-24 also creates flat lighting because the light on the left cancels the modeling of the one on the right. In low areas where neither flash reaches there will be dark voids.
The better strategy for revealing the natural 3D shape of macro objects isn't any different doing it on larger one and you have the clues for doing it in these shots. Getting "natural" looking modeling with artificial flash in macro shots is simply a matter of first finding the camera angle relative to the object and light that models it well in the natural light then add your flash from the same angles: Key light from above and behind, directional frontal "fill" lighting from sightly above the lens (like natural downward skylight) not completely flat.
Not wanting to buy macro flashes I devised a DIY modifier which allows me to light my macro shots with my existing pair of 580ex flashes as described above. See: http://photo.nova.org/MacroDiffuser/ which works well with a single flash in the hotshoe by itself or in combination with a second flash behind as shape defining rim lighting.