The title page is part of a book's front matter. The problem, of course, is that the concept of "page" in an ePub is slippery. In order to create a good-looking title page, some publishers embed a title page image. My question is, what size should this image be?
I am not referring to the size of the cover; that is a separate issue.
There are no size constraint as such for images ( eg . title page or any other image), however it is preferred to have high resolution images.
Note : Just make sure if the book contain too many images, due to high res images epub size should not become too heavy.
Secondly make sure as a best practice following styling is carried for all images
All images width should be 100%:
img {width:100%;}
Bind every image inside a holder to control the size of the image as required:
div.imgHolder {
width: 85%;
text-align:center;
display:inline;}
The title page can be as big or as small as can be. There are no technical constraints about the size of a title page image -- other than that of interior images generally. An image is also optional -- I have produced ebooks without any title page images at all.
For epubs which will be converted into Kindle format, generally you should provide as high quality of an image as possible and then let Kindle downconvert images according to the size of the display.
I'm assuming that you are editing HTML and not using MS Word or Indesign. If you do, here's the css I use which makes Amazon happy. See Stretching an image to fit the screen
