Are you able to change the description of the chair etc... that the algo makes when it hatches? I think you should be able to so that the chair ,etc.. fits in with the theme of the manse/craft.

Yes, you certainly can. The cost is the same 50 credits as with any item customization, and you can change the long and short descriptions.

The fulcrux of Avaerin (my algontherine) has a glowing emerald orb, rather than a regular hovering shield one. I don't think you can change the actual noun itself though - it has to be a chair of some sort.

All you have to do is email artifacts@lusternia.com to request the customization, and HELP CUSTOMIZATION gives further details.