Sprite sizes etc

Hi everyone, i was just wondering what the maximum recomended size for a game sprite is - i know there's probably not an official size but i'm just wondering what general rule of thumb other users keep in mind when designing games so they don't slow down and that sort of thing.

You see i plan on making the sprites for my game in a program called anime studio, using painted images animated in a cut-out style, reduced and then imported into MMF 2.
Naturally i want to keep as much detail as possible in the sprites however i do realise a lot of detail is going to be lost and i'll be painting with that in mind- so far i've animated an arm and imported it with pleasing results but the arm alone is 56 pixels tall so the main character would probably be about 150 pixels tall.Would sprites that large or larger be too much for MMF to handle? I'm not planning on having hundreds of sprites on screen at the same time - too get an idea think old school Castlevania - i don't think they ever had too large a quantity of badguys on screen at any one given time but some of the bosses could be quite large thats the sort of thing i'm aiming for.

Also if it's not asking too much (and my post is getting quite long winded by now,sorry for that)what screen/window size is recomended for maximum compatability between computers?
the reason i ask is because one of the biggest mistakes i made in a earlier MMF project was to build my game to the exact dimensions of my computer screen which rendered the entire application useless to some - and i only realised once i'd finished too!.

Any assistance or opinions you can offer on either of the above subjects would be much appreciated,Thankyou.

As for the sprites, it really depends on a few factors. First and foremost, what screen resolution you are targeting, and what exactly sprite in the game you are making. For instance, obviously, a boss character typically is a lot bigger than your player and other sprites in the game. Generally, I do my work within 64x64 for the entire character. 32x32 works best for probably 640x480, but I find it hard to put the detail I want in a 32x32 sprite.

As for resolution, that depends on what the final build is going to be. For instance, I have planned a couple games I will use the Flash exporter on once it's available. For those, I'm targeting 640x480 res. I think I read somewhere that 1024x768 is one of the most common desktop resolutions. Ultimately though it depends on how you want your game to look and what size of sprites you are making. For desktop games, I'd target probably either 800x600 or 1024x768. For web based games, I'd go 640x480 tops.

You can target other resolutions, but you have to keep your audience in mind. Personally, I run my desktop at 1920x1200, but a lot of people won't run their computer in either widescreen or nearly as high of res.

For future reference, does anybody know how switching between multiple resolutions would be handled? I assume there is some sort of display/system extension that can switch resolution, but I don't know how it handles aspect ratio.

Wow that was quick, thanks for your response - sounds to me like the dimensions you use and i'd guess alot of other MMF users probably use them aswell pretty much match that of the ol' Super Nintendo Entertainment System. I was initally planning on conforming to those myself i suppose now what i'm really wanting to find out is whether using higher res sprites is gonna come back to bite me in terms of memory and speed or whether just sticking with the dimensions you mentioned might save me from any trouble later down the track.

I Don't suppose there is anyone with high-res experience that might be able to help out?