It also makes it simple for the graphics guy to make whole new images as and when marketing have the need. Doing it your way, thought technically better, would require the assistance of a web designer.
Looks nice, but from a HCI and Disability Accessibility PoV this is a big problem. I have some points that I hope will help you.
Firstly, the text is not searchable (by bots or humans using browsers), and this is a big issue for users who are blind or sight-impaired. Screen readers cannot accurately read text from images, and therefore you place this category of user at a distinct disadvantage [see the DDA section 4.7 p39, 5.23 (p71) and 5.26 (p68)].
Even sight-impaired (versus blind) users are at a disadvantage because they can no longer change the font to more a easily readable one, and enlarging an image pixelates it - often making it more difficult to read.
Furthermore, some users have problems distinguishing certain colour contrasts, and by making the colour, font and background unalterable, you prevent them from being able to change this to something more suitable for their condition.
For something such as a logo, this isn't important content and you should simply provide "alt" text that shows what is in the picture. For these new items you should _minimally_ do the same, but ideally fix it properly.
To give you an idea, open your site in Firefox and go to view -> page style -> no style (and turn off image loading). The site should still make perfect "sense" in a semantic sense, and all of the same information should be there
.
Disclosure:
I am a sw engineer, in cloud etc, but touching on the web stuff.
hth
