Text message background image issues

[Lacey_Underalls]

I recently cleared the cache in the messaging program as a suggestion to an issue I was having. The issue is resolved, but it cleared my settings (text bubble type, background image, font size), which I expected. I'm trying to add a new background image, but no matter what I download, it becomes pixelated and distorted after it's applied. Any tips for how to improve upon this (i.e. best image size for background)? I don't recall my previous image looking this distorted. Thanks!