How can I make my bedroom look nice?

So I'm tidying my room fully tomorrow and usually when it's really tidy and nicely hoovered, it's really lovely. However... I want a really minimalist room. But I have so much I need in my room and so little space. I have my piano, desk, bed, wardrobe and floor space for dance but I need it all there. I can't provide images, unfortunately, but I just want advice for making rooms like really nice. I have posters by my bed and they're tidy, they're not scruffy. But I have cracks in my ceiling which is what I hate. I'm sat there at night looking at these lumps and cracks on the ceiling from where I have plastered over them. The rest of my room is really fine.

Any suggestions for those annoying bumps and cracks on my ceiling, there doesn't seem to be much I can do seen as they're like lumps on the ceiling which can't be cut off or anything...