I think a really nice patterned quilt or bedspread. Try and strike a nice balance between your mums taste and yours. Make it like a little retreat for her... Include some nice hangers in the cupboard and a spot to pop a suitcase up... Like a nice wide ottoman or a wooden slat bench. I don't know what they are actually called but I picked one up second hand and they often have them at hotels. Maybe also put up some old photos of you and your mum from when you where a kid. I've seen framed old toys too... I guess just some touches to show your mum she is welcome and honoured. I have a few bedspreads and linens I inherited from my parents and my parents in law. I always put them on the bed when the respective parent visits. A dressing table would be nice too. With her own sets of toiletries. I would include in the cupboards extra blankets, a dressing gown, slippers, some extra coats and the sorts of things that the she might forget or not want to bring every time. I think its more about the little touches. What colours would she like?

Agree with @dohraime, look at next size up. I always buy the next size up in quilts/doona covers as well, so there is a bit more overhang on the sides.

I have been looking on Houzz and got a couple of ideas for the bedside tables (without spending anything!) .. Please let me know your opinions on the following... Attack the existing ones with a sander and take off half of the white paint, exposing the dark brown underneath, and making them look like they are meant to be shabby. Take them both out of the room and replace with a stack of vintage suitcases on the door side and an old weathered timber folding chair on the window side (got these in storage so wouldn't cost anything!). The chair would have to have something on top like a box to hide the usual bedside table clutter in, I guess. 3. Any other suggestions? Don't want to spend any money here if I can help it! I have access to plenty of old pallets which people seem to make amazing things out of but don't know if that would be too rustic in this room?

Beautiful guest room, it has a great energy and guests will love it! I would keep the framework and just change the mount to white, the metallic frame works in with the warmth of your existing timber and adds that extra texture balance. Another small bedside table will create more balance, I would replace the bedside lamp with something softer and neutral. 2 x more pillows with a light grey cover and one rectangle or round scatter cushion at the front will frame up the space well and bring some more character and life with a throw at the end. I would work with warm light greys and perhaps something soft as an accent like brown or dusty pink for the scatter cushion/throw. Well done :)