A brilliant energy shield (with or without spikes) will not harm nonliving creatures or objects.
The reason I say this is that the shield (without spikes) is the significant part of the weapon. When you add spikes, it improves the effectiveness of the shield as a weapon. The spikes themselves are not the weapon.
Benefit: These spikes turn a shield into a martial piercing weapon and increase the damage dealt by a shield bash as if the shield were designed for a creature one size category larger than you (see “spiked shields” on Table: Weapons). You can’t put spikes on a buckler or a tower shield. Otherwise, attacking with a spiked shield is like making a shield bash attack.
An enhancement bonus on a spiked shield does not improve the effectiveness of a shield bash made with it, but a spiked shield can be made into a magic weapon in its own right.
Source: Core Rulebook
Not another shields as weapons for enchants thread ... oh well.
Honestly, your first concern is 'why am I spending the money on a lousy enchant when I could instead get just a +3 or a flaming/frost/corrosive enchant?'.
In this case ... as the spikes 'turn the shield into' a new weapon, the brilliant energy would cover the shield as a weapon too. So your shield bash against a skeleton turns into effectively a forearm smash. It then becomes a shield for blocking purposes later because magic so the skeleton gets blocked from clawing you back.
Yeah, the +1 flaming frost corrosive shield just sounds cooler too even without the game rules behind it.