- False, exaggerated reports via radio or television
- More violent police
- Better organization between gangs and others against police
- Worse reactions to initial video
- Larger, more influential gangs directly against the police actions
- Involvement of more neighborhoods in Los Angeles
- Natural disaster occurs during unrest (unlikely but possible)
1) The exaggerated reports would be a big deal in getting a major response. There are two potential avenues that can be run with - either white Los Angeles residents great really angry and the join the rights, or they get very freaked out and start defending themselves with guns, as shop owners did in Koreatown.
2) More violent police wouldn't need much. Just one case of a cop doing something really stupid, caught by the news media would be enough.
3) This wouldn't do much. The police were well-organized, and they got thousands of reinforcements from the CHP within 24 hours of the riots kicking off. Better organization among rioters would likely just cause more reinforcements, not bigger riots.
4) I don't know the reactions could get worse. You had people during the riots saying "If they ever do that to my boy, I'm a put a hit out on them." Between this and what happened to Latasha Harlins (16-year-old girl shot dead by a Korean store owner in 1991, store owner never went to jail), the black residents of Los Angeles were as angry as they could possibly get.
5) See #3. Against National Guard troops and Marines, the gangs haven't got the ability to make more problems than they did. Early on, against LAPD officers, one could have the gangs cause many more dead and injured police, but once the troops are out, this is largely irrelevant, because gangsters, as dangerous as they are, have nothing on armed troops.
6) This is the biggie. The bigger the riots, the bigger the mess is going to be. IOTL, the rioting was largely confined to an area running from Long Beach north towards downtown LA, and west of the beach - Venice, Santa Monica, Marina del Ray and several other seaside neighborhoods were largely spared, and the Valley and the eastern parts of metro LA, as well as Orange County, were quiet. Make that mess spread across that distance, and you've made one helluva huge riot.
7) LA is relatively immune from natural disasters aside from earthquakes and forest fires. One option you could have is to have screwups cause more problems - a stolen truck is hit by a freight train and causes a derailment spilling toxic chemicals or causing big explosions, for example, or a freaked-out pilot in a smaller plane is hit by an airliner going in or out of LAX causing it to crash. (That happened in an LA suburb in August 1986, when a Aeromexico DC-9 and a private Piper Cherokee collided over Torrance, CA, and both planes crashed, killing 82 people.) Have the latter happen between a heavily-loaded 747 and a business jet early in the riots and you not only add hundreds to the body count, you'd likely set at lot of areas on fire as a result, just when the LAFD is stretched to the limit trying to stop rioter-started fires.