Does anyone know if you can "animate" backgrounds? say have multiple images and they alternate (like an animation)
You can animate a background much like what you recently completed with the water in your Donkey Kong Jr. pack. Below is an example of code that would be used in the hires.txt file for a title screen (although, you could change it to apply to a level). You would basically use the background conditions in conjunction with frameRange conditions. The "TitleScreenCheck" in the example below was also used to look for a tile unique to the title screen. If the game finds a tile in the position specified below, the condition is true. This is one possible way to distinguish backgrounds depending on the circumstance.
Keep in mind, the way things work in Mesen is that once it finds a match and replaces graphics for something based on conditions, it basically stops looking for that particular graphic. In other words, put your most restrictive conditions at the top of the hires.txt file and the least restrictive conditions lower.
#Title screen frame ranges
#Title screen animation
Also, it looks like things are coming along with this latest project. Have you considered lowering the color count for the background image to make it fit a "retro" look? If you are using Photoshop, you can achieve this by converting the image format to "RGB" (under "image", then "mode"), then switch it to "index," and under "Palette" you can select one of the "local" options. Then, you can experiment with changing the number listed in the color box to achieve the desired look. It will look more pixelated (and may have dithering depending on your settings), but that may fit the graphic style a little better. Below is a quick mockup that could use a little cleanup, but I think it helps with the general idea.