Nokia allowed people to receive 72x14, 1bpp pictures over a series of binary- or hex-encoded SMS messages, and have them show up instead of their carrier name on the home screen. In the 2000s, magazine ads and webpages would distribute them using premium-SMS.
This service, also featuring ringtones, games etc. has been revived, free of charge, by MtF hacker @[email protected] of the Chaos Computer Club. You can go to Blåmba.de and download all kinds of content into your retro phone.
The service has been discussed in detail at her 38C3 talk: media.ccc.de / YouTube mirror
I also made 10 logos mostly related to Blåhaj, these are already in the Blåmba logo repository.
I welcome feedback and suggestions for future logos!
Flood-filling with a pattern is very easy on a technical level, even Nokia 3410's picture message editor can do that automatically. You lose half the resolution by area (pixels are basically √2 bigger on each side and in a 45° grid) to get a shade of grey. The hard part is knowing when such a sacrifice is worth it and when not (not often for a height of 14) and to guess or A/B test which phase of the pattern preserves most detail. Sometimes you want more complex dithering or even combined with an outline like the glossy FreeBSD logo.