I actually get the decorative purpose part. It makes sense. Decorations tend to collect dust and just somehow disappear in plain sight. Or in extreme cases, until someone writes "clean me"
So to hang up something like this for the sole purpose of decoration, I understand that it's absolutely not okay.
Same goes for any charms or whatnot, that's absolutely understood. Eg. Hanging ayatul kursi and saying this is being hung up to protect my home: I don't think that's okay but please correct me if I am wrong.
The shirk elements aside, where is the line between decoration and remembrance? Intentions are prerequisite, but is that all? Probably not, right? I hope someone here can shed some light on this.
Example:
There's a picture in the hall and it contains words or even entire surahs or allahs name(s), etc.
Let's say something simple.... الحمد لله
A child stares at it, the parent explains it, child grows up remembering this, انشالله implementing what it has learned
A visitor, no knowledge of any kind about islam, arabic or Islamic teaching, questions the image and good conversation is then sparked. Best case, you've opened someone's eyes that islam is not what the media portrays
One's own self, in a mood of some sort, sees image, is reminded instantly and visually of their (re)actions and remembers to mind their tongue and just be thankful
Just examples but you get the point. Does that still classify the said الحمدلله as a decoration?