Creating mixed media work always provokes questions like "What am I looking at?" and "How did you make this?" I ask these questions too, and one of my favorite questions to ask someone is "Why did you make that decision?", which gets to the meaning behind the method. Without going into a technical tutorial, I'm going to show you some of the materials and strategies I use with an emphasis on the storytelling effects I'm going for with my handling of media. Hope this gives a glimpse into my process.
My main point in this post is that I like my environments to reflect the psychology of my characters--as though what we are seeing is through the eyes and emotions of the characters. Some level of abstraction is necessary to attain this. Image has to depart from the real in order to become metaphorical. It's amazing how we can pick up on this unconsciously and how it guides our experience.
Above is a typical page from Splendid-Lite. It has multiple panels and in terms of materials is all over the map. The first panel is hand drawn and painted with dry and wet media, but the image on the screen was a picture of a painting on canvas that was added in photoshop. The blue mist was done in watercolor, but was also added later. I do this kind of thing a lot. Sometimes the atmosphere is a drawn or splatter-painted element and sometimes it's photographic.
Here is a glimpse of the same area of the page but with the dominant panel removed:

The second and third panels are a fusion of mixed media figure drawings with photos of a miniature model drive-in movie set that I constructed in my studio. The images on the screens are slides of paintings that were projected onto a vintage, portable, movie screen, which is playing the role of the drive-in screen. This washed out the images in a believable way, like the photos were shot at a real drive-in. The idea is to balance aspects of the real with the artificial.
Below is an unaffected pic of the drive in set. The lighting is high contrast and dramatic. The concession signage is backwards because it was made of old time, printing press blocks. In the final images, I affected the backgrounds with lens blur filters in pshop because, while I want the setting to have a nice ersatz feel, I wanted it to have a bit of mystery. I mean look at those toy cars. They look like....well....they look like toy cars. While I want them to feel a bit artificial in the final image, and perhaps even look like toy cars upon close scrutiny, I don't want them to shout "Hey! I'm a toy car!"

In the page below I used a different type of juxtaposition to achieve a similar psychological effect. The panel at the top of the page was invented from scratch with no reference. In a story where the majority of figure drawings are from life or photo refs, invented images take on a particularly interesting psychology, as though they reflect quite purely what is happening in the characters' minds. Just as extreme close-ups are commonly used to show intense emotion, I think this insertion of conceptual drawing in a realist comic portrays extreme psychology.

The atmosphere behind the drawing is a watercolor wash. Here's what the top of the page looks like without the drawing:

The words in the background are meant to represent an excerpt from one of the character's lab journals.
The bottom part of the page is a combination of two drawings of a house. One of the drawings, the one you see the majority of, is a mixed media drawing from a picture of an actual location. The other drawing was a hand-made collage of photographic and hand drawn elements:

The two drawings of the house were combined in photoshop during the layout.