Single Latest Posts allows you to display thumbnails for posts, however your theme must support them. Optionally you can specify the width and height for thumbnails – please note, WordPress just crop images it doesn’t allow resizing (so images don’t lose their proportions) -, once your images has been uploaded these values won’t work if they are superior to the size of the thumbnail already registered, you must regenerate them with another plugin if you want to change this.
This plugin also includes placeholders for posts which doesn’t have thumbnails. There are three (3) different options for thumbnails fillers: placeholder (by default), kittens, puppies and optionally there is another one which you can set through the Single Latest Posts Settings page.
[slposts thumbnail=true] // Display thumbnails [slposts thumbnail=true thumbnail_wh=80x80] // Crop thumbnails to 80px by 80px [slposts thumbnail=true thumbnail_filler=puppies] // Sets puppies as thumbnail filler [slposts thumbnail=true thumbnail_class=alignleft] // CSS class for your thumbnails