Mostly PNG, as it is lossless and supports alpha channels. Usually, .gifs will often suffice, especially for online content, but it is very much dependent on the clients' needs. Unfortunately, .gifs do not have alpha support and can cause colour issues due to compression, so do keep this in mind. In terms of scaling, always be aware that to get clean lines and keep a consistent pixel size, you will want to scale by factors of 100, and using the Nearest Neighbour interpolation method. I personally work on a 240x135 for projects that require a 16:9 ration, and upscale by 800% for the final 1920x1080 resolution.
I usually gather all my files in a zipped folder and then Deliver to the client. The files included in that depends on the project, like for animations, it is mostly gif scaled up and in original size format and the sprite sheet of all animation. If client demands seperate Pngs of complete animation, I include that too. For the backgrounds and static sprites, I deliver a High quality PNG and original size PNG file. I also include the photoshop and aseprite files in all of my deliveries.
I am regularly working with .ase files (aseprite) and bouncing those down into GIF, PNG, JPG, WEBM, SVG, PSD and other formats that are requested by clients. I regularly use 256x144px for full screen scenes. which I can scale up by 1000% to 2560x1440 When posting to Instagram/TikTok I will use smaller resolutions like 108x135, 108x192px I use around 50px and below to make smaller assets which can be scaled up to whatever specific size that is needed for clients.
I usually deliver my work in PNG and GIF formats, sometimes providing sprite sheets for animations. I use pixel perfect scaling when required and prefer to work in 'power of two' ratios as it gives the best results when scaling. Most pixel graphics I create are optimized for use in low resolution games so I generally design sprites in 16x16, 32x32 or 64x64 and a full screen background is typically 320x200 (similar resolutions to old computers and consoles)
I usually deliver my files in the png format. Resolution depends on the subject. Sprites and items are usually delivered around 512x512 px, while single portraits are 600x600 px. Group portraits at their maximum (as in 18 figures) are 576 x 289 px.
Scaling and the original aseprite file are included for no additional charge.
My standard delivery includes PNG files along with GIFs to demonstrate the timing of animations. For smaller pixel art pieces, I also provide a version that is approximately four times the original size. This allows clients to evaluate the details and quality of the artwork without having to enlarge it themselves.
File format tends to be PNG for the lossless compression. Resolution is dependent on the project requirements. However, I always maintain the same Pixel Density throughout a project whether it be working with a team or on my own.