Ahh yes, trends…let me think back a bit…these will be in the order i remember them, and is probably very jumbled up, but they were all trends at one time or another
- Violent/unpleasant death
- Insanity and suicide causing items
- Human SCP
- Biological SCP
- Household items that do extraordinary things
- Mythological/Religious SCP
- Clockwork things
- Guys/Items What Fight Good
- Large scale SCP items, like buildings and areas of land
- Body horror
There is no way to predict a trend. I can say, however, that one good entry can set one off. 076 opened the door for human SCP items. 914 introduced the concept of "variable result" items.
If you want to try and direct the site, or create a new trend, here's how you do it: Find a totally new concept, or use a preexisting one better then anyone else has. Next, make sure your entry is solid, feels real, and creepy or interesting as hell. If all that is place, and it strikes a cord with the community, you may touch off a trend.
I admit, i'm not a fan of trends, but only when they run too long. If 5 to 8 SCP pop up with a "family resemblance", it can actually enhance the site, as long as they are based on a good concept. It's when 15 or 20 pop up that it starts to be too much. If i could have my way, everything would be totally original, but a few trends and imitation now and then is very understandable.