Comment 1 for bug 726009

You can circumvent the problem at the "import" stage: at this stage, you can choose how many images OpenShot will play per single image of the original sequence.
That way, you cannot speed the sequence up, but you can slow it down by a factor 2, 3, 4 etc. by telling OpenShot to play 2, 3, 4, ... frames per imported image.

If you are not happy with the result, you can remove the sequence from the project and re-import it with a different choice.

I agree, however, that the speed should be modifiable for image sequences, as it is for a usual video clip.