Ah, I see, I assumed that every character more or less has a profile picture already and you may wish to customize the bar for everyone. Should've cleared this from beginning, sorry.
If you only use one image, that brings up another matter: what with the text? If you don't edit the image, then To, From and Subject fields lose their point altogether, as they need to be changed from transmission to transmission.
So, alternatives are as follows:
1. Generic image in placeholder (where Noctis sits currently), generic text in text area (signal strength, decoding, and other spam; probably From: field, too, if you plan to have all transmissions to come from one source).
Pros: easy to start using for new members, easy to post.
Cons: needs all transmission details typed separately, all bars are identical.
2. Character-specific image with generic text. For new members, a few easy steps must be one to export a new bar for them with pic of their choice (.psd I can provide).
Pros: easy to identify who's the sender, easy to post
Cons: a bit of work for each new member, details still need to be typed separately.
3. Character specific image and text for each transmission embedded in the image.
Pros: no other details required separately, custom bar for each transmission
Cons: quite a lot of work of adding text and uploading image for each transmission. Requires an image-editing software and to have the font installed every time it's used.
I'd personally suggest options 1 or 2, depends how many members you have, whether they have character pictures and whether you have access to image-editing software (I can make bars for each current member with images provided, but you may wish to be able to work independently further on).
Till further notice I'll work on generic everything, to see how it looks.