This could be simple, but really helpful.

For whatever reason . . . maybe USB keyboard and USB mouse with Fedora 12 KDE Live version etc. is at the core of this really but . . .

Is there a way to change picture size in Gwenview other than with the scroll bar on the bottom
the mouse is so jumpy. . . I'd rather just type in . . . say 125 %
rather than scroll and the bar jumps from say 110% to then 143% ?

Thank you very much.

Unfortunately this is not possible at this time. You may wish to file a feature request at bugs.kde.org.