PSA: If you're trying to create a Snapchat Geofilter using the Photoshop PSD file and you find that the PNG is larger than 300kb, you can use https://tinypng.com/
to get it under that file size limitation. Snapchat says it must be < 500kb in an error message but it actually has to be < 300kb.
The image you use should be 1080px wide. Leave a 149px buffer at the bottom and top of the template.