Rejoyce, all ye who have suffered the plight of the solid white background on GTA Online crew emblems! One of the most requested bug fixes in the history of Rockstar's multiplayer open-world crime romp has finally arrived to the joy of all players. An issue that has caused many a vehicle to become an eyesore has been fixed, hopefully once and for all.

But first, some explanation. If you're familiar with online multiplayer games, you'll know that the vast majority of them have some kind of affiliation system integrated, though the name changes on a case by case basis. Guilds, Clans, Factions, Orgs, or in the case of GTA Online, Crews, are (generally) international persistent groups of players which act as a team. They all represent their Crew and strive to further the crew's agenda. Crew-mates play together and tend to help each other out.
While the importance of these affiliations differs between games — in some cases, they are involved in the core mechanic — they don't have too much significance in GTA Online functionality-wise. However, they are more than important for the community.
While the hacker issue on PC has been solved, and hackers are still unable to get onto the current gen consoles, the Xbox 360 and PS3 are still pretty much infested. Plus, there are griefers and assholes everywhere. As such, playing in the crew-only private lobbies of your own team will ensure a non-toxic environment.
Crewmembers can represent their crew by emblazoning their Crew Emblem on their vehicles. Each GTA Online crew can create and upload, via the Social Club, a special icon or image that becomes the Crew's logo. There are a few decency rules, but the administrators of Crews are generally allowed to get creative.