The VSE is well designed to do a simple task like this, and you can do an OpenGL render if you are impatient! ;-)
You can make a blender project with predetermined dimensions, eg 1280 by 720, making a vertical narrow image.
All media dragged into the VSE will "Auto-resize" to fit these dimensions.
Drag in an image, select it and press Ctrl-G to make a metastrip. We
will re-use this metastrip in a stack. To change the image simply
open the metastrip and replace the image strip.
Select the metastrip (right click) then press Shift-A (Add) > Effect Strip > Gaussian Blur. Set Blur value to x: 50 y: 50 for example
Duplicate the metastrip Ctrl-D and move it above the effect strip.
You can constrain the horizontal movement by pressing the y key.
Select the 2nd metastrip (right click) then press Shift-A (Add) > Effect Strip > Transform. Change the scale of the y: 0.5 (this
depends on the original image aspect ratio).
With the top effect strip selected make sure that it's 'blend' type
is set to Alpha Over or Over Drop.
With all this done, you only need to swap the contents of the metastrip to change the effect output. To open the metastrip just press TAB. And TAB to return to VSE master timeline.