Your eBay photos are your strongest advertising resource in your listings, so picking your camera for your eBay work is important!  There's so many features to choose from and each camera model varies in megapixels.   Did you know you don't need a high megapixel camera to get great photos?   An expensive camera is not essential to get a great eBay photo. 
 
So, how do you choose?  First, you'll need to understand what a megapixel is, to determine which camera you want to buy.  Digital photos are made of pixels, which you can think of as dots.  A megapixel is one million pixels (or dots).  The number of pixels a camera can capture is called the resolution.  So, a camera resolution is how many megapixels it can record in a single image.  Just because your camera can record 3 or 4 megapixels, doesn't mean you have to use the highest settings for photos that will be displayed in your auction listings on the web!  In fact, photos that are 2, 3, or 4 megapixels would be much to large to upload efficiently and view in your listings.  Huge photos also take too long for your buyers on a dial-up connection to load.  Many buyers are still on dial-up connections, and you want to be sure your photos are not so large, that they will click to another seller's listing, instead of waiting for them to load.
 
Most newer digital cameras allow you to adjust the size of the photo you take.  Here's are some common size settings from higher resolution to lower resolution:  1600 x 1200 (Large), 1024 x 768 (Medium), 640 x 480 pixels (Small).  The "Small" setting is sufficient for eBay, and a 640 x 480 photos is just one-third of a megapixel.    Here's an example.  The "small" 640 x 480 pixel photo below is a common size for a full-size or the supersized/enlarged photo.   At one-third of a megapixel for the image below, you can see how even 1 megapixel camera could work for your auction listing photos.
 
 
 
Higher resolution cameras are more expensive than lower resolution digital cameras.   Using higher resolution cameras or settings can be slower, when saving the digital photo to the memory card, because when you use the higher resolution settings (1600 x 1200 Large or 1024 x 768  Medium), it takes more time to process and compress and then save this higher-resolution image to the memory card.  The higher resolution photos use more room on your memory card, so it will hold less photos.  Also, once you transfer your photos to your computer, these higher resolution photos are much too big to use, and you need to resize them so they are suitable for your listings.  As you can see,  you can use a higher resolution camera or setting, but you don't need to. 
 
Take a minute to look at your camera manual to see how to change the photo size, and try taking your photos on the Small setting.  Many cameras allow you set the size and compression.  For instance, you could choose "Small" photo size and "Fine" compression.
 
So, when do you want to use the higher-resolution photos?  Higher resolution photos are perfect for printing.   Lower resolution digital photos will be fine for viewing on the web, but will look grainy if you print them.   If you'll be printing or ordering prints of 4x6,  5x7 or 8x10 photos--not just viewing them on eBay--you will want to set your camera to a higher resolution.
 
Some other features you want to look for are the ability to set the "White Balance" and to set the exposure and aperture with a "Manual" setting.  A timer setting is also helpful.  Many sellers aren't happy with the quality of their photos, and think that getting a camera with higher megapixels is the answer.  Most likely, it is how you are taking the photo, rather than the camera itself.  Do you have adequate light?  Are you using the flash and the color looks bad?  Are you using a tripod?   Are you using the digital zoom rather than getting closer to your subject?  There's many things to consider when taking a photo that can affect the quality.
 
Here are some links where you can find helpful photograph and camera information and recommendations from knowledgeable eBay sellers: