1. A game looks better if the sprites are in the same style, or at least similar styles. People are more likely to use your sprites if you make a set with matching styles. (Doesn't mean that a single sprite will never get used, of course, and ultimately you are doing this for free, but it's something to think about.)
2. You should post it in the Creative Commons forum. Basically, creative commons is a set of descriptions of how your art is allowed to be used (i.e. free products only or commercial products allowed, edits allowed or not, credit required or not, etc). It makes it simpler so that you don't have to list out the rules yourself, you can just name or link the accurate license.
This forum post has links to the creative commons licenses that can be used for VN assets. If you don't want to use a creative commons license, there's also the
Free to use but not CC subforum. If you use this forum, you'll have to list out your restrictions on how the material can be used. (Although, a lot of people who post in the Creative Commons section don't actually list a creative commons license, so this isn't really a hard rule.)
3. Art assests being too small is definitely a problem. Assets which are too big can at least be resized with a little bit of knowledge of an editing program. I'm not sure what the average size for a sprite usually is. Maybe take a look at some other sprites and see how big they are? And if you're caught between two sizes, pick the bigger one.
Also, I like the sketch - a lot of the free assets are high schoolers in school uniforms. Anything different from that brings some much-needed diversity to the Creative Commmons section. Good luck!
