Abstract long exposure, fourty seconds clouds moving

Tried to combine two 20 second exposures of cumulus clouds today, and by the time I set up all of my photographic equipment, it was dark to so extent. I would like to post my results on Flickr and other photo sharing sites. I pushed the levels of the image to about the maximum level, but that unfortunately resulted in far too much posterization. This was the best that I could do because of the poor lighting. I had pretty much only two options before creating this abstract: to use no filters, which would result only up to about 1/20th of a second, and the second choice was to use my 12 stop ND filter which is what I did. The ND filter resulted in a 20 second exposure. It was very late in the day, and the lighting on the clouds was too flat and so I had to push various image settings to the extreme. I like how it looks, but to the vast majority of people out there this is probably not a desirable photo in term of aesthetic look.

This is a moderately zoomed in photo of the major severe storm that was over Southeast Michigan today; such clouds can create for incredible photos using the correct gear and while the lighting is correct. This subject matter and long exposure are two things that have made me excited, especially if there's lightning flashing around me in various directions and windy!!! I really wished for this photo to have turned out far better, even though the experience was exciting to some extent.