Trends change on what seems to be an almost daily basis. What is in fashion one day is out by the next week. This is also true of housing trends. Right now, what is most desired is an open floor plan between the kitchen, living room, and dining room. Many apartments do not have the capacity to create an open floor plan, but for those that do, it is something that you may want to look into. Modernizing your rental property is often a fine line, but it does certainly have its benefits.
When you're working on keeping up with newer trends in regards to housing, it can seem almost impossible to change as quickly as people's ideas of what they want do. Sometimes, however, certain trends have already changed and have stayed the same. For example, if you remember the light pink and light blue colors that used to be so popular in bathrooms, you'll find it isn't quite desired anymore. The same goes for many designs of wallpaper or brighter colors of paint on the walls.
The unfortunate thing about keeping up with trends is that it doesn't quite matter what you like when it comes to designing. Something that you may enjoy may not be the best idea to place in a rental property. Ask around with other rental property owners who have recently updated their space to see what they did and what worked for them. Keeping up with trends can be exhausting, but it is certainly more than worth it to see the improvements that your tenants can and will enjoy.