Those are some tasty looking drinks. Well done there. Beyond that I'm not clear on what you're asking. NPC size is 32? Do you mean 32 pixels by 32 pixels? What does the size of NPC's in your game have to do with the cocktails?

Oh, you're talking specifically about the LPC set! 

I don't believe there is any item size specifications for the LPC beyond the fact that most tiles are no larger than 32x32. That is assuming these are not equipment items that show up in the character animations?

The NPC's and other characters are not 32x32 though. They are 32x48 (or 48x64 including all equipment, clothing, and margin for animation). See the official LPC style guide for more information: http://lpc.opengameart.org/static/lpc-style-guide/styleguide.html#charac...

Only in that they must visually make sense on the base and not extend beyond the bounds of each frame of animation. See the https://opengameart.org/content/lpc-medieval-fantasy-character-sprites clothing and weapon spritesheets as examples. The clothing layers are separate from the character base, but they move and adjust position as if they were on the naked character base. This allows each layer to be stacked on the base spritesheet to complete the fully clothed and equipped animation. However, if a weapon (like a long spear) exceeded the bounds of the sprite frame (48x64 typically) then the tip of the spear would be clipped from one frame, but appear as a phantom floating spearpoint in the next frame.

Awesome to hear you're interested in making stuff in the LPC style! A few other things that may be helpful:

- For sprites, there was originally a "Universal Spritesheet" repository here https://github.com/jrconway3/Universal-LPC-spritesheet which attempted to compile all the different clothing, weapons, etc. into a single spritesheet, so you could assemble sprites by turning on and off layers in GIMP. That hasn't been update in a while, however there was also a web app allowing you to do the same thing graphically. People keep making new versions of it, see semi-recent discussion here: https://opengameart.org/forumtopic/lpc-updated-spritesheet-generator . I think this is the most recent/comprehensive version, which is by castelonia: https://sanderfrenken.github.io/Universal-LPC-Spritesheet-Character-Gene... . 

- For non-sprites, there's some additional useful information about style, size, perspective, etc. in the LPC style guide that MedicineStorm linked if you scroll up (and down). For the drinks you drew for instance (which look really nice!), you'd probably want to adjust the perspective a bit so that the top of the drink is also visible. 

Let me know if you have any questions, I've spent a lot of time with those assets. 

have you tried altering the sprite of the character itself instead of creating a new hat sprite.
Or if the hair of a sprite is a separate object perhaps replacing that with the hat object. If you want to keep some form of hair then perhaps draw some hair to go along with your hat. I dont know how LPC works but Im pretty sure either of these will be your best bet.

Can you show an examples of the sprite clipping through the hair? If the hair is taller than the hat, it will clip through the top (assuming you're layering base -> hair -> hat), so you'll need to adjust that in your engine somehow. bigbeargames was working on making masks for every hat to get rid of clipping hair; see https://opengameart.org/forumtopic/lpc-updated-spritesheet-generator?page=1 .