Getting right to the point, here's the character I was aiming for:
and my rendition (The shoes were the only part of this costume I already had and didn't need to make):
I don't really know what I used for patterns. The skirt was altered from a simple Burda magazine pattern to have a wrap around, and the top (except the strap) came from one of the strapless dress patterns I have. I combined the two together into a dress, added all the black bands, the strap, and sleeve (altered from yet another pattern).
One thing that bothered me about the design itself is that the "kimono" crosses the wrong way. It should always be left over right, but the Sims designers have it crossed the way a western women's garment would.
The most difficult part of the whole thing was probably the obi. I started out trying to make it look as close as I could to the Sims' screenshots I had, but it wasn't working. In the end I took it all apart and re-made it the way a tsuke obi is put together. I hand-dyed the orange gradient onto yellow fabric - that part was pretty exciting.
I also constructed the plumbobs for both our costumes using the template from here printed onto card stock then painted and wired to a headband. I made 4 total so we could change our moods while wearing the costumes at ConnectiCon (red, yellow, green, white).
I get pretty serious about accuracy sometimes. For the thought bubble we carried around, I digitally traced screen shots of it and the symbols to get the shapes and scale correct. The symbols were printed on card stock and the bubble traced again onto foam core, then everything got painted since I printed in black and white. The woohoo heart is the only one that came out the wrong scale, and the alien is made with cut paper instead of paint. They're all on velcro so we could change the thought on the bubble.
If you would like to see a couple more photos (though not many), check out my craftster post.