Random guesses about Love and Lust:
- Less conflict (Love)
- More marriages and children (Love)
- More lovers (Love and Lust)
- More extra maritial affairs (Lust primarily)
- More master/student associations (Love, without any sexual connotations)
- Fewer murders (Love)
- More murders (of competitors, Lust)
Apart from that (and other things, of course), they'd also serve as opponents to the influence of other spheres. Some might not be head on opposition but rather at lesser angles, if the analogy makes sense. Similarly, they may modify other spheres.
- Love vs Hate
- Love vs Strife
- Love vs War
- Love vs Arrogance
- Love combining with Lust
- Love combining with Passion
- Lust vs Lethargy
- Lust combining with Hate and Strife (separately or combined)
- etc.
Spheres may also affect people's values, so people within a sphere's influence might be nudged toward aligned values. This can also be effected by making scholars within such influences more prone to write books promoting those values and less prone to write ones against them. Effects don't have to be obviously visible in the open to still affect things.
Another interesting sphere, conceptually, is Depravity. According to the sphere relationship data, Lust and Depravity are more closely associated with each other than they are to any other in-game sphere, with Depravity being opposed to Laws.
What I'm thinking is that Depravity is the act of defying socially-acceptable behavior, while Lust is the motivation that causes one to do so. It doesn't have to be exclusively sexual lust; lust can be for money (theft) or violence (murder/assault). So maybe when a creature evaluates whether it will perform an action, its urges are pitted against its values.
A god of Lust could increase the strength of urges, while a god of Depravity could decrease the strength of values.
Orrr Lust could be exclusively sexual, considering that there doesn't seem to be another sphere specifically associated with sex.