I love what you've done so far - I would, however, change the light frame to a black one and add matting that is the same colour as the red in your hallway print that will tie your hall way and dining area together in a subtle way as well as making the print bigger - you could take the matt out by upto 15cm (more if you're brave) and the frame width of between 2cm up to 10 (again depending on how brave you are). As it's a rather large wall you can go bigger with the matt and frame as your wall can take it and you've been restrained with the rest of your colour and material pallet. Your plants are lovely but they're lost down on the floor in the corner - if you can boost them up (I've found pots turned upside down work and have also been known to use old pottery sewer pipes painted - they're totally clean of course!) so that they're a feature rather than an afterthought.

Zazzle.com.au have some cool and affordable posters you can then frame with IKEA / KMart / target frames etc... try searching graffiti for something edgy or beach photography for some Cali type images... or there's architecture shots too. There's multiple sizes available and you can then try matching up to frame before purchasing.. Good luck

Agree with above comments - large rug, darker colours to balance the beige. And I also think the art work is too small and too high. However if you are attached to these pieces they could be hung together on one wall, lower, maybe re-framed in similar frames to give them cohesion (black to match your new cushions?). This would create the effect of a larger art piece. (The centre of your art should be at average eye height - and in that room you are sitting so eye height is lower!)

You could consider custom joinery that actually looks freestanding - purposefully creating a gap from the edge of the fireplace surround to the wardrobe & on the wall side also. This would also mean that it really does not matter if the front of the cupboards do not align with the front of the fireplace. Adding a nicely detailed leg, and a feature handle (you can get some really unique Australian made ones these days) to give some visual interest to the otherwise minimal finishes. Keep it simple & classic so it ages with your child's taste and preferences. As an example, The Design Files recent article has an image of a cupboard in a lounge area, that could be adapted to two double door units on either side of the fireplace https://thedesignfiles.net/2019/10/interiors-house-p-cjh-studio/. Seems perfect for a child of any age, or even if you want to convert the room to a more 'grown up purpose' once they leave home ;-)