in your first post with pics i don't see to much of a problem with the grout line thickness as this would take an extremelly eagled eyed person to notice 1mm of a difference,however i'm not sure if i can see adhesive spread over the walls between(this may just be the photo playing tricks) the tiles meaning 1 of 2 things
1-your tiler has spread the back of each
tile(totally fine)
2-your tiler may have dot and dabbed each
tile(not good)this can be checked by knocking each
tile to check if they are hollow sounding behing them.
your mosaic pics don't fill me with confidence but as TJ said i would wait and see if they had slipped after the tiler left,he will sort them immediatly as this has happened to us all before.also maybe ask him if there is a thickness difference in the
tile and mosaic and what he can do to accomodate it.i personally have done jobs where customers have asked for feature mosaics to protrude from from the field tiles and also customers who ask them to be flush,maybe asking him what the builders specifications asre on this or is he using his own experience on what he thinks is best here.
the last pic does show the grout lines differing quite dramaticall and this would be cause for concern and may be worth raising as an issue with the tiler