OP, can I ask about your process? Like what tablet you used, how long it took, and how you approached completing the illustration? It's something I've been wanting to get into.
It's going to sound ridiculous, but, like almost all of my digital art, I used a mouse for this, not a tablet. Here's the step-by step process:
1. I made sketches of each dinosaur in Photoshop without any background (a mistake I won't make again) and fully rendered them in grayscale. each dino is on it's own layer. Made sure the dinos I chose to be in the picture were all from the same time period and region (For example, you can't pit an Allosaurus against a Postosuchus, that's just foolishness). I rendered scales with a combination of the basic paintbrush tool and the basic scales texture brush.
2. I thought of a background that would fit the lighting angle and contrast on the grayscale paintings.
3. Did research into paleontology regarding the flora and landscapes at the time. Had a difficult time finding anything about the landscapes of prehistoric Alberta outside of forests (which couldn't have made up the entire region) so I just stole a kind of wetlands background idea you'd see in a todd marshall drawing because it looks cool and hoped it made sense.
4. I painted the background in color, including the sky. Realized that I really, really liked the clouds in this one jpeg I used as a reference so I just used that and altered it a bit with the paintbrush tool instead of using my own sky painting.
5. I figured out a color pattern for the dinos and colorized them by going to: adjustments > color balance, brightness/contrast, hue/saturation
It took about 12 hours on and off over the weekend(I work slow)
That's basically it.