Use whatever image hosting service you like and post the link to /r/woodworking. The key here is it needs to be apparent that you've built the entry, and you follow the photo requirements listed in the contest rules. Submissions of finished photos only will not be accepted for entry. <-- I can't emphasize this enough, you absolutely need more than 2-3 photos for a valid submission. I will no longer accept entries that have albums that go from rough stock to 90% complete in one jump.
Natural Light. Natural light is best, so any windows that offer illumination to the space should be put to good use. If you have little sunlight in your shop, locate your workbench so that its work surface gets whatever there is. Even the best eyesight is made better by good light, so the close work to be done on a benchtop benefits from the natural light.
Let’s be clear about one thing: No workshop is perfect for everyone. If there were, I could simply give you a precise plan to follow with clear dimensions. Every person who comes to the hobby, avocation, or profession of woodworking has his own particular collection of tools and his own peculiar work style, skills, and desires for the kind of woodworking he wants to do that gives him a unique approach as to how he will lay out a shop: where the tools should go, where lumber and supplies are stored, and how much bench area he needs.