
blahpers |

Wild shape is a polymorph effect. Other polymorph effects do not work on a creature already under the influence of a polymorph effect. Furthermore, size altering effects also do not work on a creature under the influence of a polymorph effect, so that rules out things like enlarge person and animal growth. Though the latter is also ineffective because a druid using wild shape doesn't change type to animal; ergo, they are not a valid target for the spell.
Polymorph effects can be confusing! Read up on them here.

Scott Wilhelm |
What works with Shapechange?
Enlarge Person
Animal growth
Metamagic Feats should work on them okay. Those are Spells, and should work with Metamagic Feats like they say they do on the label. Some of them wouldn't work. I don't think you could Maximize a Spell that doesn't inflict or cure damage, for instance.

avr |

Just in case you mean the spell shapechange and not the druidic ability wild shape - shapechange can have the extend spell metamagic, brisk spell and a few others, but generally only via metamagic rods. Shapechange is a 9th level spell and if metamagic raises it to 10th level or higher it can't be cast.