Homepage Recommended Image Sizes
Resolution
All images should be optimized for the web at 72dpi to lower the file size as much as possible prior to uploading to WordPress. This is the single most important thing you can do to improve the performance of your site.
File Type
For most cases you should be using .jpg files which have a lower file size than .png files. Only use .png files when you are using transparency.
Size Recommendations
Around Town Featured Images
In this section the consistency in both the width and height of all images is important.
Featured Deal Featured Image
The height of this image is not critical. If you keep the aspect ratio at 4:3 or 1:1 (square) it will look best.
Blog Section Featured Images
The height of this image is not critical. Having the images at different aspect ratios for different posts can look nice. Some people like the consistency, however, so if you want everything to look very clean, use the recommended height below.
Meet A Mom Featured Image
Again, the height of this featured image is not important, but I have seen a lot of sites use a portrait image on here (aspect ratio 1:4 for example) which does not look good. As long as the image height is not greater than the width you will be in good shape.