Is the problem the dinos or the riders? I'm sure I've seen something similar using British cavalry mounted on GW's "Cold One" creatures
Something I'd also like to do....
In this case the lancer resculpt shown at the top of the thread. I want to alter the legs and get rid of the silly unicycle, then mount him in a howdah mounted atop a Triceratops as the handler. Add a hook to the lance so it can be used to tug on the horns etc to guide it. Essentially a big one of these;
I have a couple of Triceratops and will probably do a similar thing with other medium sized dinosaurs.
For my lancers I have 10 of the new Dark Elf cold ones which are slowly getting their armour altered to fit in better. I have Renegade WW1 British cavalry in gasmasks to be their riders, although I'm going to have a go at giving them hats.
Most of my cav will be Frontier Light Horse, when Empress eventually release them, mounted on 1/35th Tamiya Raptors with a crest and tac added.
I also have two 1/35th Brachiosaurs, they're expensive but fantastic models. The intention is to have a side slung troop transport on either side of them.
Then there's the T-Rex I picked up which is a great model, don't remember who makes it off hand though. I keep having the idea of putting armoured crew on it, but may keep it as an independant.
Finally, aside from the infantry, I have a raptor handler using a Westwind adventurer and a group of HLBS mini raptors.