Oddly-shaped shower stalls do not have to use a conventional shower rod. If you have a shower with a 90-degree angle at the outside corner, treat it like you would an inside corner with windows on both sides. Specialty L-shaped curtain rods are available from decorating and window treatment shops. Look for a waterproof material for your shower. Install the hanging brackets directly into the wall above the shower surround at the end portions of the walls. This type of shower rod alternative should be used if the shower is in an L-shaped alcove with a wall at the end of each of the short sides.
Don't try to conform your shower rod to the L-shape of your shower. Install a straight shower curtain rod from the corner of each end of an L-shaped shower to make the third side of a triangle. Putting the shower curtain at an angle to the shower makes your shower appear larger when you have the curtain closed and keeps the curtain from being pulled into the shower from air drafts.
You do not need to buy custom-made rods for your shower curtain. Use two wide window curtain rods connected with a corner connector. This lets you install the rod with a right angle in the rod where you need it. Add more rods attached with corner connectors to make the curtain go around an L-shaped shower with only two sides against walls. Connectors are available wherever window treatments are sold. Keep in mind that you will likely need to add support for the curtain rods from above if you choose this method. Install hanging brackets from the ceiling at the corners of the shower rod to hold it in place.
As a last resort, if you cannot locate a means to install a shower curtain rod on your 90-degree-angle shower, add a pair of sliding or swinging doors that meet at the corner of the shower. If one side of the shower is longer than the other, install a door on that part, and leave the other half a fixed piece of glass. Framed and frameless shower doors are available from bathroom design stores to match the type of decorating theme you have for the bathroom.