- Body part "library", with date of collection and features of each source creature listed on index cards;
- "Cold Room", where ice and snow are brought for shaping simulacra;
- Cages of failed experiments.
Those with Delayed Blast Fireball would be seekers of pure physical force; they would have an arsenal of wands and staves for their unique attack spells and testing ranges to see the full capabilities of each instrument of destruction they create. They will be seeking Meteor Swarm and Prismatic Wall as their ultimate goals.
Those with Reverse Gravity like to distort the physical and might have permanent test areas for gravity, time, and space warp effects. They will be researching Time Stop and Maze.
Those with Limited Wish are on a quest to eventually acquire a full Wish, and their towers would be filled with the results of botched wishes as they investigate the limits of what can be wished for.
Wizards who command Words of Power might be more interested in subtle and overt control. Their laboratories are probably simple chambers that can hold masses of people without allowing their escape. They may also research Symbol and Mass Charm.
Wizards who have Phase Door are probably interested in the ethereal state and investigating the solidity of matter. They probably already know Dimension Door and Teleport, and they are researching new ideas along those lines, including Gate and the Astral Spell. Their towers will have many chambers without doors.
Those with Charm Plants have a plant fetish and may fancy themselves druids, even if they aren't. They will have arboretums and gardens and sun rooms, and animated plant servants or guardians. They probably also have quirky higher-level versions of Massmorph.
Msss Invisibility seems like it would primarily interest a wizard with dreams of conquest. Why else would they need to make 100 to 300 men and horses invisible? They will have other spells relevant to conquest, and will probably match either the Delayed Blast Fireball mage or the Word of Power mage in style and temperament.
Those with Monster Summoning V probably have the lower level variants and are seeking the higher-level versions. They will also be interested in ways to keep summoned monsters around longer, and may have a retinue of very exotic extra-planar creatures, with zoos or lairs to keep them in.
Those who eventually attain the 8th level Polymorph Any Object spell will be interested in transmutations of many sorts. They may have objects made of exotic substances: glass swords as strong as steel, floors of solid air, columns of water that defy gravity. Some of their retainers will be humans transformed into powerful monster forms. They will be researching Shapechange.