I have recently been practicing a modified version of the first exercise in IIH.
essentially, I imagine a thought, and hold it, but it evolves along my direction, like a film screen.
But the thought itself is held at long periods of time.
For example I have used the following exercises:
An unfolding rose
A rotting corpse
A Castle being built stone by stone (this is very difficult)
A Palace of Crystal growing organically
A mushroom growing on a log
Cooking a meal in my mind, for example, imagining a pan, and then adding noodles and vegetables in one thought-sequence
I am not sure if this is very effective as theoretically it is not 'fixed' on one thought, but it is fixing my Stream-of-Thought in one place.
I believe there are Tibetan Buddhist practices that are similar, involving building Bodhisattva Palaces with flowers, Buddhas and jewels, but I haven't managed to find any information on these specialist visualisation meditations thus far.