Allow me to summarise the suggestions:

The automatic chameleon circuit functions as an automatic camouflage. It changes its camouflage due to different biomes, surrounding blocks, and manual override. For example, when the TARDIS dematerialises in a small wooden hut in a taiga biome, it actively changes its camouflage to a mantelpiece (I've got little imagination:p)

 You've kinda got the idea, but I never said different biomes. I meant, it will automatically change its exterior appearance based on what is most around it so it will disguise itself best for where has landed not its biome.

Looks like I'm supporting one of your suggestions this time around. I really like the concept here, and I hope to see it in game.

One thing I think could be discussed a bit further in the OP is how the Tardis analyzes its surroundings and chooses an exterior.

What are the criteria and deciding factors that go into choosing? Block count within an area? Nearby structures? Biome type?

 Biome doesn't matter, I was thinking a 200 block radius and it checks for all structures/blocks around it to disguise itself as well as possible, these structures could be trees, player built buildings, etc. And how it analyses it, I've not actually thought of that yet, I'll get back to you on that one. :) I'm sure you knew it'd be a matter of time until I found something good to suggest. xD

Factors that decide TARDIS exterior:

1. Scans to determine if the TARDIS is indoors or not.
2. If outdoors, scan for external features of terrain within 200 blocks of range (for example trees, ice pillars, mountains, gravel roads and villager houses etc). If naturally spawned, it changes its exterior based on structure spawn rates in each individual biome. If not, determine whether the TARDIS is in a city like area or rural area based on number of artificial block within range, then determines its exterior based on the data.
3. If indoors, scan for number of naturally-occurring blocks in range. Determines if the TARDIS is in a building or underground. If in a building, scan for building style and change exterior accordingly (if in a gothic church, changes into a podium, if in a modern building, changes in a pot of flower or painting) If underground, determines if in a cave or mineshaft or base, changes accordingly.
4. If underwater, instant dematerialisation to nearest place without water to prevent player drowning.

 Tbh I'd already kinda touched on the factors right above you but I do actually like some of that idea. I think I'll add some of that to my suggestion a bit later.

Bump

i think the indoor/outdoor thing would be kindof hard to pull off with coding, or the furniture for the different type of building,  but i do like the idea

 What do you mean by "indoor/outdoor thing"? That's kinda confused me, and the idea is that the tardis checks about 400 block radius from where it is and then chooses the best thing to disguise itself as depending on what's around it most and where it is, then it will choose the exterior, whether it's a tree, fireplace, clock, pillar, chunk of ore, etc.

like telling if the tardis is indoors or outdoors, was reffering to JH's post

 Oh, I was kinda thinking that idea would be related to the scan in the radius, where depending what's around it so if it's in an area surrounded by something and there's lots of stuff in it like chests and stuff then it'd know it's in a house or something and to disguise itself with something most in the place it's situated.

Bump. Thread updated. Finally got round to it.