If your new Miva Merchant store has a ReadyTheme installed like this Base ReadyTheme, you'll be able to make some light customisations to the look and feel of your store with just a few clicks in the Admin.
Here we have a placeholder image for the store logo and we can swap that out with either some text or a different image of your choosing. To swap out this image with text, go to the ReadyThemes area in your Store Admin. Under the look and feel section, change logo type from Image to Text and then type in the name of your store. You can also choose a tagline or enter a contact phone number. After you've made changes, click “Update” to save your work. When you go back to your store and hit “Refresh,” your logo will update to reflect your changes.
If you have an image for your logo, you can upload that too. Go back into your Admin and make sure logo type is set to Image. From here, click on the “Select Logo” button, click on the “Add” button and choose “Upload Images.” Browse to the image that you want to upload and click “Choose” and then click “Select Image.” After you've uploaded your image, just click “Update” to save your work and when you go back to the store and hit “Refresh,” now you'll have a nice image for your store logo.