Since you're new to the forum, you won't be able to post the pics, but space out the letter h t t p s when you post the link and rosemow (who is the sweetest most helpful person in the game) will fix it to post your pics or I or one of the other forum members will.
Most importantly just have fun! Everybody who participates gets a Maxis fave nom, so just do you stuff and show them your creativity and skills. It's also fun to see what everyone else comes up with room wise.
And there are other building challenges on the forum. Build n' Share runs one (these are judged) and Quality Control has a room challenge (judged) and a lot challenge (which is just for fun right now so everyone gets a Maxis fave nom). Just like the One room thread, these threads are also in the Lots category of the Creative Corner. I think there are also Sim making challenges too.
Hope you have fun! You're a very good builder/decorator, so these challenges should be great for you!