Here is my second attempt at posting on the blog :)
For design some concepts you could consider might include an easily customisable range of templates. Some possible ideas for designs would include changing fonts, backgrounds, foreground objects, etc. If there are several options for each design class then you would in theory have several hundred or more unique designs.
Some common themes for marriage include flowers, running writing, pictures of the bride and groom, etc. Some examples of templates used by another site with a marriage theme you can see here: http://www.mydreamshaadi.in/sample.html