One of the things I found that helped me feel more comfortable was to outfit the bathroom in "male colours". I chose a nice blue, brown and teal pallet that allowed me to feel like it was mine and masculine, but not overpowering. It made me far more comfotable than the mismatched set of towels etc that had been collected from people gifting me (all pinks and now very faded purples). I'm not meaning to say that any particular colours are male or female, I just made it feel mine by how I wanted it to be 🙂 (My bedroom is white, grey and purple - except the walls are brown because I haven't painted from the previous tenant).
Just make it scream YOU and it's YOUR mancave!