I do like the idea of there being ruins scattered through the island so Emet can have more painful nostalgia I mean uh. For research. Yeah.

Re: climate/terrain, I vote deciduous, aka. mountainous/foresty.

It could be interesting to I think theme the island loosely with lunar references. Like 'moon and star'. So we could combine the idea of a volcanic caldera being the main focus (the 'moon') and have smaller islands dotted around it as the 'stars' which the crew could inhabit. These islands could be floating or elevated or whatever suits people's fancies. The hidden grottos and lagoons would also add to this.

(Proposal: curving partially around the volcano's base is a big lake that is in the shape of a crescent moon.)