My sprites are the Sprites of Lizard
The Lizard editing tool I showed in Update #6 has a very basic pixel editor that can be used to make graphics tiles for the game, but I it also has the ability to export and import tile pages as regular image files, so that I can work with more powerful graphics tools when I need it.
Because my tool only works on small 8x8 pixel tiles, for editing larger images I often use GIMP, which is a free and open source image editing program. It's very powerful, but it has a steep initial learning curve. One of the things that helped me find my way with GIMP was this excellent pixel-art tutorial by Matej Jan.
For animations, I like to use Aseprite, which is an excellent pixel-oriented animation tool. Older versions are available for free, but even the current version has a very low price and is also open source.
To efficiently create sprites for the NES, you need to think in terms of 8x8 pixel tiles. Every sprite is a collection of these tiles pasted together, and it is important to realize that they do not have to be arranged on a grid. You can animate a bobbing head just by having one head tile and changing its position between sprites, for example.
I managed to fit this dog's animation set into 46 tiles. There are many sets of unique legs, but very few tiles for the upper half of the body. This makes the upper part of the body look a little bit static, but I thought the tradeoff was acceptable in this case. I often have to make judgement calls about whether I want to conserve space (for more creatures) or consume space (for more detailed animation).
The 10 sprites of the octopus here used a total of only 32 tiles. If you look at the tiles used (in the part of the window called CHR) you can see them all contained in a rectangle at mid-right. Note that only the left half needs to be tiled, because the NES is able to flip sprite tiles. Creating symmetrical characters can help a lot with this.
Ultimately, not just the look of each creature, but the way they behave as well is motivated by a desire to keep the tile set small. This is one of the many ways that the NES will assert its influence on you as a developer.
I recently had a long chat with J.A. Laraque at Obsolete Gamer. If you'd like to see me ramble at length about games and music, you can watch it here.
I was also interviewed by David Giltinan for Read Retro. You can read it here:
There are only 6 days left in this campaign. Thanks to everyone who has helped it come this far!