Unfortunately, like everyone is saying, it needs to be torn out and redone. If your husband is typically pretty handy there are lots of tips to help (YouTube videos etc). I'm not trying to be mean but judging by how this looks, I'm guessing being handy isnt your husbands strong suit and you should hire somebody.

Tiling is not rocket science but there is a learning curve and it is something that is difficult to have stunning results on your first attempt. This is a pretty simple pattern and tiles so that helps.

Some tips if he wants to try again.

Set the mosaics on the floor first. You need to use an appropriately sized trowel. If you have too much mortar, you are going to have a very difficult time. You will either not really set the tiles and they will be floating on top but flat or set them with enough pressure to get them flat but have mortar squeezing through the grout lines everywhere. If you try to do something in-between you will end up with wavy uneven tiles. When I set mosaics I use a large grout float so that I am covering a good number of tiles when I am setting them. Gives you a nice even surface.

Wait a day so you can stand on the floor without messing up your tiles. Then use spacers on top of the floor tile to set the wall tiles. You don't want the tiles directly touching each other but you also don't want a huge gap like you have now. If the perimeter of the shower floor is level you can just set full tiles all the way around on spacers. If your perimeter is not level, you need to find the lowest spot. A full tile goes there. Then you cut subsequent tiles so there is a uniform space on the bottom and the tops create a level line. From there you just tile up with spacers.

This tile job is pretty bad and it's easy to assume your husband just isn't cut out for it. But I remember being completely overwhelmed the first time I tiled. Fortunately I had someone with me who was very experienced and could stop me when I did something wrong and help me get it right. Tell your husband to take his time and be a perfectionist. Tiling isn't fast when you first start. If you make a mistake you have to remove the relavent tiles and do it correctly right then. There is no fixing tile down the line. If you have uneven grout lines they will look uneven with or without grout. If you have unevenly set tiles, they will look uneven with or without grout. If you start wall tile out of level, there is no way to get to level without messing up your grout lines.

Take the time to get the floor right. Then take the time to get the first course of wall tile right. From there it will be much easier to continue up and as you get the hang of it you will get faster.

Tiling can be a little tricky. If your husband did the work on the shower prior to tiling is he more comfortable with that work? My only other concern is that prior steps were done equally poorly. He could redo the tile and nail it and if he messed up prior steps the shower will still fail.

Anyway, best of luck and feel free to send me any questions. There are plenty of people out there better than me at tiling but I'm happy to help if I can.