I love to throw themed dinner parties (which just happen to correspond with our favorite types of foods). Here are some of the ones we have had in the past:
Asian themed...
What you need to make it work- think zen- basically anything natural or earthy (e.g., wood, bamboo, stones, orchids, etc.), chopsticks, oriental spoons (if you are having soup) and place cards that bring it all together.
French themed...
What you need to make it work- think french bistro- red table cloth, basket(s) for bread, carafe(s) for water, small candle holders and chalkboard place cards.
Indian themed...
What you need to make it work- think bright and colourful- a really funky tablecloth (e.g., orange and pink), bright coloured flowers, reflective candle holders, some type of unique figurine(s) (e.g., elephant, etc.) or decorations (mine were gold coloured Christmas ornaments hanging from the chandelier).
I try to use the same white dishes for all the themes, just change up the accessories. I get most of my accessories from thrift stores- recently I have had the most luck at Value Village. We have a small house so to keep myself from going overboard, I limit myself to only enough accessories to fill one of the baskets in my kitchen. I have 4 baskets in total so I have one more theme to come up with yet- I am thinking Scottish...