This plugin allows you to edit images directly in the WordPress dashboard, including adding rounded or oval edges.

2. Image Hover Effects Ultimate:

This plugin provides options to add different image effects, including rounded or oval edges, when users hover over images.

3. Custom CSS Plugins (e.g., Simple Custom CSS):

Although not specifically for images, you can use custom CSS to apply rounded or oval edges to images across your site. You can add custom CSS like this:

```css
img {
border-radius: 50%; /* For circular images */
border-radius: 25%; /* For oval images */
}
```

Simply adjust the `border-radius` percentage based on your desired shape.

4. CSS Hero:

This plugin allows you to easily customize your WordPress theme's styles, including adding rounded or oval edges to images without needing to write custom CSS.

Using these plugins or CSS, you can achieve the desired oval edge effect for your images in WordPress.