Wordpress
2.1 has come with some really nice updates, however, like the previous versions, there is still one problem with the images.
I feel the thumbnail image in Wordress is too small for my taste’s and so i need to be able to adjust the image size automatically when uploading into the system. The maximum image was 128px width.
In my older Wordpress, I was using before, the size for the thumbnail creation could be changed in the inline-upload.php. You can view my post about How to Resize Thumbnail Image in WordPress. But now, this file has disappeared.
Don’t worry! You still able to edit thumbnail size in Wordpress 2.1 
The size for the thumbnail creation could be changed in the admin_functions.php.
Just open the file and search for:
$max_side = apply_filters( 'wp_thumbnail_max_side_length',
128, $attachment_id, $file );
and change it to:
$max_side = apply_filters( 'wp_thumbnail_max_side_length',
256, $attachment_id, $file );
That will double the thumbnail size like mine 
The disadvantage from this method is you need to edit “wp-admin/admin_functions.php” file again when you upgrade your WordPress version, because the new “wp-admin/admin_functions.php” file from the newest version will overwrite your “wp-admin/admin_functions.php” file.
Hopefully, in an upcoming WordPress release, they will give us a preference on thumbnail sizes.
Have a great day!