Why is my phone no longer showing picture backgrounds in start? (W10M.)

[Windows Central Question]

My HTC One M8, updated to W10M developer preview latest build, won't show picture background in the start screen. It used to, but for no apparent reason it decided to show only accent color as live tile appearance. I verified all settings are correct to show pictures in the start personalization settings. Moved back and forth between personalization options, restarted the phone, went through a OS preview version update and searched the web for people having the same issue. Couldn't find a single solution. Any suggestion? Thank you.