We’ve rented several different houses that had bathrooms with no storage space — just a pedestal sink, a toilet, and bathtub. Here are some storage solutions I’ve used over the past.
We thought it was odd that one older house we lived in did not have a toilet roll holder already installed. Nor did it have a place to hang a towel by the sink. Rather than drill into the plaster/concrete walls, we opted for an over-the-tank toilet roll holder. We also installed a Command towel bar. Command, the experts in damage-free hanging items, has a large selection of products for bathrooms such as a wall and cabinet organizer, hair dryer holder, accessory organizer, and soap dish. They are amazing products, especially for renters who may not want to drill holes in walls when moving in or fill holes and repaint when moving out.
While we opted for a plastic rolling cart (similar to this one) for storage under our pedestal sink, a neighbour used pedestal sink shelves with a collection of little baskets to keep her things in order. I like this narrow cabinet with pull out shelves. It would be handy in a small space, but being made of wood, it would easily suffer from water damage if a toilet or sink overflowed. A standing corner shelf might be better option.
I’m not a fan of storage over the toilet. I’ve had the misfortune of smacking my head on cupboard doors left open and losing my hairbrush and cosmetics in the toilet. Also, some cabinets are installed so low that they must be removed if the toilet has to be repaired. That being said, storage over the toilet can be a great space for items not accessed frequently such as extra towels, toilet paper, tissues, etc. Perhaps a cabinet with sliding doors would be a better option for this space.