I've lived in a lot of apartment's. As a kid we lived in apartments until I was about twelve and my mom always did little things to make it feel like our home. Even in my college dorm room I did things to try to make my little space feel like mine.
I've spent my adult life living in apartments and the one thing I've learned is you need to make it yours. Many of us treat an apartment as a temporary living space because you may move out sooner rather then later and, well, it's an apartment.
I'd suggest ditching the temporary mentality. I can't tell you how many people have thought they would be in a place for one year and then five years later and they still don't have art on their walls. When you move in, move in and make it yours.
I've taken a few years to make the changes I've made in my home. I like to live in a space and see what will work. Plus my style has evolved over time and I like to explore new things in my home.
The one thing that will have the biggest impact is paint. Most leases will state what you are allowed to do. If you aren't sure if you can paint then check with your landlord. They may stipulate you need to paint it back when you leave. They should paint between tenants anyways, so there shouldn't be a problem.
I lived in my apartment for three years hating the paint color. It was beige and had these jaundiced yellow undertones. I finally painted it a light grey and it made such a difference. I can't believe how much time I spent hating my house. I also painted my fireplace because the red was just too much and it wasn't my color. I did check with my landlord first and he gave the OK.
Here's the before-
Temporary wallpaper is everywhere these days. I got mine at Target! I cannot yet attest to how easy it comes off. I'll report back, because knowing me I'll want to change it out. The very top paper shows a subtle temporary wallpaper I used. While the wallpaper below was a little bit more bold.
I highly recommend going for something bold in small spaces.
Another option is to use paint canvases. In my bedroom I hung three large canvases behind the bed (I got them on super sale) and it adds color and pattern without having to paint the walls. Here's the how to.
If you don't feel like getting out the paint brushes, I get it. Definitely make sure you decorate and design your home so it feels like you. Hang your art, find a beautiful rug, and get some plants. There are so many small ways that you can make your house feel like your home. The main point is to not treat your home as a temporary way station. It's your home, so own it (at least temporarily!).