Snapchat now allows companies and groups to create geofilters for users to add to their snaps when they are at an event or specific location.
There are two different options for geofilters.
The Community Filter
These are free filters used for cities, universities and other public locations that artists are encouraged to create and submit for free.
The On-Demand Filter
These filters are used by businesses and individuals to highlight an event, business or location.
How to create an on-demand filter for your brand or event

1. Design the filter. Create a web ready .png that is 1080px by 1920px. You cannot include contact information, urls, social handles or hashtags, but you can include your logo and other brand trademarks. Other guidelines here.
2. Go to snapchat.com.
3. Use the map to select a time and location for the filter to go live.
4. Purchase the filter and submit artwork for approval. This usually takes about one business day.

Make sure to promote the filter before and during the event to encourage people to use it and spread awareness for your brand and event.