Below I've given a brief overview of the vehicles in my army and how I added some small bits and bobs to fit them into my army's theme.
As with the Squad Sergeants, I painted dinosaur and dragon symbols on the hull of all my tanks. This has the added advantage of breaking up the black colour otherwise dominating the model. Painting freehand on vehicles is much easier than on banners due to the flat surface and extra space for larger images.
Apart from the small horns added to the exhausts and dozer blade, I fitted Tyranid carapaces on the front track guards painted up to resemble scales. It's important to add adornments that are large or to group smaller ones like I did here, as well as painting them up in a contrasting colour. This brings out the decorations, otherwise they might go unnoticed!
The Land Speeders had cardboard stegosaurus plates fitted on the ridge between the crew seats. While it might look slightly inpractical, it really enforces the dinosaur theme. By painting the plates a deep green colour they blend in with the rest of the vehicle, otherwise they might've stood out too much. This is important to remember when painting 'stuck-on' vehicle decorations, like banners or sails.
The remaining vehicles of the army have all received the same treatment as the Rhino, with Tyranid bits added to them, as well as freehanded details.