Featured - for Flutterbat only.
Bat Pony - Any bat pony or oc pony only.
Mature - Only naughty picture of Flutterbat.
Bat Pony Mature - Any bat pony or oc pony in naughty only.
Base - Any base pony for bat pony.
Vector - No idea that mean, but I am sure you know where this mean to you.
Crossover - any character that Flutterbat join with other character didnt belong to MLP.
Other - Just random picture.