When dealing with larger scale games, getting the sprites to look good at multiple resolutions is important. For many VNs, each sprite is only given a small amount of time, leaving each sprite to result in less overall quality. Even worse you can have sprites with bad crop jobs, featuring bits of color bleed past the lines, or worse, into the transparencies.
The solution to this, is to finish your sprites at very large resolutions, and optimally all lineart and color should be completely digital. This is of course limited by your computer's RAM. However going as large as you can while maintaining proper speed with enough layers for all your colors is a necessity.
For sprites and most line art based images, I use SAI.
|Whether you start the sketch traditionally, or digitally, it is important that at your linework is high enough quality at the highest resolution you can manage.|
This is the Aunyrae sprite at 100% resolution. The final sprite base is 5000x tall.
For example, to facilitate any resolution that might be necessary, all sprites that I have done have started at 5000x tall like Aunyrae. In Sai this resolution gives me good flexibility in how many layers I have with only 4gb of Ram (most production artists for VNs work much, much higher, sometimes twice as big, with 16gb of ram+) I consider 4gb of Ram to be the normal, given how extremely cheap Ram is today, you should have similiar capabilities to me. But this is still very ram intensive, and it's advised you do not have a browser open while drawing.
An example of two characters, both sketch form and lineart form.
To begin a sprite I begin with a sketch signifying the BASE pose of that character. This is the pose the character will be in for most of the game. It is important that all design critique, corrections, and fixes happen in the sketch phase. If you do not have team members to consult with. It is important to have artists that you, or your artist can consult with. It is normal to redo a sketch many times before it's approved for line art. In this case, the sketch of Queen Llend is not in it's final state and it's important to go through and signify what the character's outfit might look like at all angles, and with all it's layers.
Line art is a stage that is quite difficult at this resolution. It's important that your lineart is done entirely on it's own transparent layer, and when finished it's important to lock the transparency of the layer. Accidents in coloring the wrong layer might ruin your lines!
It requires practice and a lot of scrutiny. Removing gaps and frayed lines, or avoiding them all together. This is very time intensive, and for many people it is the most crucial part of the image, as bad or wavy lines can unbalance a picture. Another reason why you must make sure your sketch has been so scrutinized at this point. Is because, once your line art is done it is very difficult to change the pose without redrawing almost everything.
The tightness of the lines makes it so that cropping lines out, re-scaling, or rotating them will ruin the lines. At this point it is very difficult to re-salvage those lines. If it's a large part of your image, you're better off re-doing that entire section.
However once this is completed, the difficulty in creating the entire sprite set decreases immensely. from this point on it is as simple as duplicating your master file, and redrawing only the specific parts of the image you need to. Such as the expression, the arms. With the hardest part being a complete pose change. On commercial projects this is more practical, where there are more artists to shoulder the burden. If you have a master file to draw design from, it is much faster to finish the set with a proper master image.
At this point you will have a very large sprite master which you can resize at will to test any resolution you could want. What is a large amount of front-loaded effort in design. Has saved you or your team massive headaches. Because you can re-scale the sprites around the game. Not having to re-scale the game to suit low res sprites.
I hope this has been helpful for people who are looking to do sprites. I admit my artwork is not perfect, but I believe this gives a lot of examples of the stages in sprite creation. As well as giving you an idea for saving yourself lots of headaches in the future by taking on one big one at the beginning.