Our assessing social worker only had a quick token look upstairs to satisfy herself that it existed and that it was "all normal" whatever that means lol.
However, the kids social worker had to see both of their bedrooms every single time he visited (a health and safety thing to check we hadn't moved them out or got lodgers in etc apparently, and a tactic used to be able to speak to older childen on their own so they could disclose anything needed is what he told us) and so they would take the opportunity to show him round and shownoff their "treasures" ranging from a special fire truck to a hairgrip they found on the street outside and snuck in to sleep with the night before. To give him credit, he usually declined to go into our bedroom when they desperately wanted to show him it, but nothing else was off limits because they had zero inhibitions about anything.
Anyway, so even of one assessing social worker doesn't go upstairs, chances are that others will at some point. I wouldn't worry too much about the decor itself, it's about whether it is safe for the child, which can look different for each one. A newborn doesn't need stairgates or toddler locks but does need appropriate lighting in the bedroom and sleeping bags and stuff. A 6 year old needs a non bunk bed but can probably do without the toddler locks on every single cupboard. You just need to be able to reassure them that you know what needs to be done and that you will do it. Then when it comes to matching panel, do it and tell them what adaptations you made. For example we noted that in our LO's profile it said he loved to climb, so instead of a key bowl on the side, we have them on a hook at the top of the door frame. Panel appreciated the specific stuff like that, and we still use it now!
I wouldn't decorate right now, but do make it so that it could be turned around quickly in case the process moves quickly.
I completely agree with @Ted27 that DIY needs to be done pre child moving in, and that is as someone who was an avid DIYer who has barely picked up a paintbrush for a year and a half. Firstly, I was absolutely knackered, secondly the kids wanted to "help" and couldn't handle rejection when I said no and finally they still completely freak out whenever something changes. We had to move the eldest's bedroom around because he needed a bigger bed, and he still asks when he will get his baby bed back. And where the old dining room table went (that he ruined by using it as a stage and making the legs go all wobbly). And why we took down the mirror frame from where he smashed the mirror playing with a ball. And what happened to the chairs he used to climb on to get to the top of the confiscated items shelving unit. He is hyper sensitive to changes in his environment, which is kinda tricky when he is a rambunctious child who loves to test everything to destruction. It's another reason I would have most major DIY done too- having stuff half done means it is more easily broken or damaged before it gets completed, and that's without having the stress of trying to do anything with them actually present!
My parents renovated our hoses constantly growing up, so we somehow sort of grew up knowing that we never touched gloss paint, or that power tools were dangerous or not to lose your balance on rafters etc. However, our kids obviously came with literally no concept of that, and there is so much else to learn so quickly with them that we just couldn't have kept them safe and us sane in anything other than a pretty much completed house. Also having a nagging to do list would have driven me mad, especially because pre adoption I thought i would have all the time in the world to do stuff on adoption leave and I was so very very wrong!
Anyway, a bit of a long and rambling post to essentially say social workers probably don't care about the decor of your house overall, but for your own sanity I would get as much done as possible, and leave the bedroom until you're more sure how it will all pan out.