Some shower ideas work best with larger showers, some with smaller showers. One of my friends was trying to come up with a casual shower theme for a friend's shower. Somehow she came onto the idea of a board games shower, which I wholeheartedly agreed with. If the group is small enough, like 10-12, you can really just set up checkerboards and play games. If it's larger, adapt some board games for a big group. (Large scale pictionary on an easel, etc.)
The invites: If you're going paper, check out these. Use a classic board game image, like monopoly pieces, or an image of the board as the backing. An image of dice, etc. There are also some cute options over at evite.
The decor: Board games set up around? Maybe checkers tabletops? Dice and gamepieces? You could also go streamers and anything colorful - nothing says cheerful and fun like board games.
The food: Anything goes - but when I was a kid, we had a kids cookbook that had recipes for domino brownies (just draw the numbers on the brownies in white frosting); you can do
cookies and put them on a checkerboard. You could
The fun: Pictionary with wedding stuff, or not. At the last shower I was at, we did wedding scattegories, wedding style - draw a grid on a piece of paper. The left axis will be wedding related categories; the top axis is either the bride's name (if it's 4-6 letters with no repeats) or just the word "BRIDE". Categories? Stuff like "things you find at a wedding" "wedding gifts" "honeymoon destinations" "first dance songs" "famous couples", etc. The usual scatergories rules apply, except you get like, 5 minutes and you fill out the entire sheet. (I would do a practice run first and see how much time is enough time.) It worked really well - although there were only like, 10 of us doing it - so if you have more people, I would break them into teams (teams might be more fun anyway, because it encourages people to get to know each other.) If you have small enough numbers, just divide into teams and play taboo and outburst and stuff.
The gifts: Board games! You can expand to puzzles if you want. Board games are great because they can be really cheap, and can be purchased anywhere. You can get really creative or be really classic, and it gives the gifts a lot of freedom. You may run the risk of getting 10 kinds of monopoly though...
The favors: Decks of cards? Poker chips? Travel board games? Those cheap games they sell at Kay Bee Toys for like, 2 for $3.
Have fun and run with it! If you have more ideas, let me know!