When choosing bathroom blinds it is really important that you chose fabrics or blind types that would suit moist conditions.
I visited a house recently about replacing their current bathroom blinds.
The first thing I noticed was the black mold on their roller blinds. The blinds were not that old but the fabric was just not suitable for moist conditions due to the cotton content in the fabric.
There are a number of options for your bathroom blinds that would be perfectly suitable and will last.
Roller Blinds are always a popular choice, and with a huge choice of fabrics that will work well depending on the level of moist / water they will be in contact with.
My first recommendation would always be PVC fabrics. They are completely waterproof and are perfectly suitable for all bathrooms.
If the blind is not likely to get wet then a fabric that has 100% polyester content will be fine for moist conditions.
The fabric to avoid is anything with a cotton content, as these fabrics get affected in moist conditions and you will start seeing mold appearing.
Vertical Blinds are also available in the same fabrics as the roller blinds so are perfectly suitable for bathroom conditions.
Wooden Venetian Blinds are incredibly popular at the moment, but are not really suitable as bathroom blinds as they are a natural timber product and will warp over time in moist conditions.
There is an option if you like the wood look and that is Faux Wood. They are designed to look just like a wooden blind but they are made from rigid PVC, so are completely waterproof making them ideal bathroom blinds.
Roman Blinds are something to be avoided as they are traditionally made from curtain fabric that has a very high cotton content. We have installed roman blinds in bathrooms but it is not a product we would recommend and we always get the customer to sign to say they accept that there maybe issues long term.