where to submit work and upload video
Our next Matte Painting challenge will probably be in April. You can always attach images to each one of your posts here via CGSociety, or host it through a free website. The best thing would probably be to submit your final image as a portfolio piece into your gallery and then embed it directly as part of your post.
Feel free to try it out before the next deadline in order to avoid any hick-ups at the end of a contest. It is also good practice to finish 24h ahead of the clock running out.