1."定时秋季"(Timed Fall)

"定时" means "timed" that's right, but "秋季"... It means "autumn".
The another meaning of "fall" in Chinese are "瀑布"(liquids fall from high place ,such as waterfall.). However I think it is still not very accurate.
Maybe it can be translated as "定时落沙"(Timed Falling Sand), perhaps it's the most accurate translation.

2."宝可梦箱"(Pixelmon Spawner)

The literal translation of "宝可梦箱" is "Pokemon Box/Chest", this is somewhat inaccurate. Spawner's official translation is "刷怪箱", so "宝可梦刷怪箱" is more accurate I think.

3."精灵宝可梦草坪"(Pixelmon Grass)

"草坪" means "lawn" but not "grass". "Grass" means "草丛" ,so "精灵宝可梦草丛" is the right translation.

These are my advice about translations of Pixelmon Mod. I am not sure that these can be fixed, but i'd like to provide more suggests.

Closing as this is expired and resolved.