OK, answer my own question, this seems to work?
>>> images_repeated = images_vec.repeat(1,sequence_length) 
>>> images_repeated = images_repeated.view(-1,input_size, sequence_length)
>>> images_repeated.size()
torch.Size([100, 784, 28])

I guess it could be checked by something like this?
images_repeated[99,783,0] == images_vec

It should be all true? I expect there must be a more robust or cleaner way to do all this though?