I think you like non-fussy, casual, kinda transitional(for whatever it means)..cozy and very livable..and you re not against some mixing and matching-you're not the style purist given all that-i think your chances on making your rental homey for you and your family are not only big-they're grand.. tie the colors together since it's a bit strange they have different color carpets in dining and living(do they? or is my monitor playing mind games with me?), with rugs, pillows since you seem to like them, change the chairs that irritate you to no end for something that you can live with(just store these ones safely), and then go slow, enjoy the process..travel..and bring things that you find while you travel..it'll be fun, and it will be meaningful

Paint the end wall. That's actually a very modern look, quite popular right now. People are taking out attics all over the place for a higher ceiling/higher utility bill/less storage. Painting the ceiling and leaving the beams wood is also trendy at the moment.

Lots of companies make fixtures compatible with older valves. I would look into changing all the fixtures (tub, shower, vanity) and a frameless shower door. Changing out baseboards and window sill/framing to something more modern (e.g 1x4 or whatever). Changing the door and doorknob will help as well. If you wanted to get more extensive, replacing cabinet doors with shaker or flat front and modern hardware and countertop material (80/sq ft so on a vanity not much $). All these types of changes are incremental and most can be done yourself without too much effort. Toilet is a standalone change. Some of these changes can be pulled and reused when you remodel. The main thing you get with a remodel 1) pull and get a modern tub 2) new floor 3) completely new shower 4) new cabinets 5) new layout But a lot of what makes modern is the surface stuff and your shower marble isnt terrible..

Idea #1 Remove the mantel legs and keep the shelf. Add an exotic granite slab surround. Install black reflective burning glass with geometric shapes and finish it off with a contemporary floating glass fireplace front. Here's how the contemporary floating glass screen looks If you post some pictures of the room so we can see the rest of the decor, I may have some other suggestions. Mockup Provided by: Hansen Wholesale Fireplace Screen Design Service