If the ceramic shelf or soap dish in your shower has cracked or broken you may want to replace it with a new one. Since this type of shelf is meant to be installed as tile would be installed, this may not be a job you are comfortable doing yourself. On the other hand, hiring someone to do it may be more expensive than you had hoped. Once installed, though, the the resulting effect is quite nice.
Here’s an example I like: simple, white, nothing fancy:
Ceramic shelves for shower pictured: Corner Shower Shelf Wall Accessory White 8-1/2″x8-1/2″ by Daltile
If you have options in terms of where to put the shelf, you should consider that water from the shower head can spray onto the shelf. This can be a problem if there is a bar of soap there. The water wets the soap and makes a puddle of soap scum on the shelf that can be a pain to clean up. Normally, the shelf has a small spout that lets water flow out.