Anyway for information, to make the portraits quick, & not feel like you are just googling faces & just paint over them, I often used
https://morphthing.com/ to merge 2 faces, & add some minor changes. Then use the result as a reference for the Portrait.
The one you said looks like Loki is the face morph of James Marsden & Michael Fassbender using the website listed above.
For the elderly man, I supplied 2 elderly men faces (that I googled) , upload them, & morph using the website, then again used as references for the creation.
Edit: I decide to make a quick illustration to share how I did it.