Helo!
I try resize an *.png:
file Mozartstr_format_test.pdf-pages_test.png
Mozartstr_format_test.pdf-pages_test.png: PNG image data, 1399 x 11811, 8-bit/color RGBA, non-interlaced
I use Kdenlive 0.7.8 (Debian Squeeze). I have in Composite Transition the Resize Option don't more as 500 percent. In Kdenlive Version 0.7.7.1 I have more than 1500 (Custom).
I need help.
Gennadiy

Hm, yes, looks like I set the limit of the spinbox rather low. I just increased it to 10000 in the latest development version.
As a workaround you can increase width and height manually.
Then the real limit depends on the actual scaler.
If it is not possible with composite try affine or the pan & zoom effect, because they use a different scaler.