It's hard to judge grout lines and flushness of the tiles from a photo, but it looks neat enough at first glance. I do see a small displacement in the horisontal grouting lines in the second pic, though that might just be a result from poor resolution in the picture. Other than that, only two things stand out a bit, but I wouldn't call the misstakes.
First, the pipes in the third pic look horrid, but that's hardly your fault. I'd cover them with something if I were your friend.
The second thing that jumps out and pokes me in the eyes, is the very small corner piece in the fourth picture from the left, but that's not necessarily an error... It depends on what the customer wants. A full piece closest to the window is preferable, but if the corner piece is smaller than 1/3 as a result of that, I'd have the customer chose wether or not to split the corner piece into two larger pieces.
If it's ok with the owner of the kitchen, then all is well I suppose.
Judging from the photos, I'd say you've earned atleast a passing grade for this, your first job 🙂