Comment # 3 on bug 815232 from Wolfgang Bauer

(In reply to tosiara tosiara from comment #2)
> This is still an issue.
> Verified, other distributions does not have that. For example, Kubuntu 14 is
> OK

Right. There's this in /etc/kde4/share/config/kdeglobals:
[PreviewSettings]
MaximumSize=3145728

This file is part of kdebase4-runtime-branding-openSUSE, i.e. openSUSE's
default settings.

But the default upstream limit is still 5MiB.
That it's impossible to change that via the GUI is an upstream bug/missing
feature I'd say.