I tried out a few free programs / apps while trying to create an animated GIF header with the above nine pictures. The simplest for Mac is PicGIF Lite. Add the stills which will make the animation, set the output size by choosing from preset sizes or make your own custom size, chose forward or reverse, choose number of frames per second then save the GIF. Included are some picture processing facilities. The only problem for me was not having the choice of no repetitions as I wanted the animation to run once only.
That brings me to my discovery of the program / app PhotoScape which is free and available for Mac and Windows. Not only can it make animated GIFs from a series of pictures but gives individual control of the timing of each frame and can make non repeating GIFs.
PhotoScape is not just a GIF maker but also has photo viewing and editing facilities,
includes collage making (one example is the top collage)
and can batch process photos.
A few trial efforts made last night:
The main facility missing is the lack of layers, otherwise there are a vast range of effects to play with. There are many more facilities in PhotoScape including text and speech bubbles, red eye removal, etc..