To say again most of the advice others already gave you :
- Improve your mini preparation procedure. This will also help you understand the sculpt, and help you decide how you will approach painting. For instance, you missed Loki's facial hair on the chin.
- Thin your paint. This is probably the single best piece of advice I was ever given, as thinned paint unlocks all intermediates and advanced painting techniques. As a rule of thumb, if a single layer is enough to get a good coverage, then the paint's too thick. 2 layers is an absolute minimum, 3 or more are preferred to achieve to good opacity. The skin parts of the wolf pelt are painted with visibly too thick paint, for instance.
- Focus on the tidiness of your basecoats. On the backpack, the red paint spilled over from the gem to the blue portion, for instance. Wolf claws are another example. Using good quality brushes will help (Raphael 8404, W&N, etc.)
- As a rule of thumb, recesses should be darker than the surrounding areas. You didn't shade all of the recessed areas of the backpack, nor did you shade the crevices in the wolf pelt skin area.
- Color are there for a reason. Why is there a white spot of paint on Loki's left boot?
- Protect your minis. If you have younger siblings that could interfere your your minis, hide the minis or place them out of their reach.
Once you've confortable with what's above, you'll be able to start considering advanced elements such as large source, higher contrasts, blending, etc.