Massmorph: This spell is used to conceal up to 100 men (or creatures of near man-size) as a woods or orchards. The concealed figures may be moved through without being detected as anything other than trees, and it will not effect the spell. It will be negated by a command for the caster or by means of a Dispell Magic spell. Range: 24".These two spells seem to fit together, since they are pretty large scale effects and both affect terrain, in a sense. Both ranges would fit in well with the proposed Line of Sight range. Both are essentially open-ended, lasting until a dispel condition is met.
Hallucinatory Terrain: By means of this spell terrain features can either be hidden or created - an illusion which effects a large area. Thus a swamp, hill, ridge, woods, or the like can be concealed or made to appear. The spell is broken when the magicked area is contacted by an opponent. Range: 24".
The question about Massmorph is: is it a transformation, or an illusion? Since it's based on a famous incident in Macbeth, one could argue it's meant to be an illusion; the spell description doesn't specify that the affected creatures are limited in any way, so maybe they can move and speak, but will be seen as trees. On the other hand, the "-morph" suffix suggests to me that this is a physical alteration, which means that, in addition to being used for a surprise attack, it can also be used to halt a small army, transforming the troops into trees. I think I'll go with the latter interpretation, but with an added twist that the "trees" can still speak to each other, but this speech will sound like the wind rustling in the leaves.
Hallucinatory Terrain throws some light on Phantasmal Forces. There's not really a limit given for the number of objects that can be part of a Phantasmal Forces illusion, but the existence of this higher-level spell suggests that the lower-level spell can't disguise an area. So, perhaps Phantasmal Forces can only create multiple copies of a single type of item that are treated as a unit. Thus, you could create a phantasmal pile of stones, or a phantasmal swarm of rats, but not a phantasmal forest... maybe just a couple phantasmal trees. Maybe a crude guideline would be a number of individual but mostly identical items equal to the caster's level?
Also notable is that, like Phantasmal Forces, the illusory terrain is dispelled by touch, but there is no mention of concentration being required. So perhaps this is the spell used to make illusory walls meant to last for years.