There are quite a few good articles available on replacing the Maximo 7.6 Title or Welcome page graphic as can be seen with this Google Search (https://www.google.com/search?q=ibm+maximo+7.6+logo). In my case, while it was easy to change the graphic, the placeholder for the image was still set to the width and height of the original image. My new image was much more rectangular in shape, so the result was a very condensed or squished image.
Changing the image is a matter of finding or creating your new graphic and changing the name to match the existing image for the skin you are using. You could edit the login.jsp page and change the name there to match your new image name but this is not recommended. The login.jsp page could, and likely will, get updated as you install patches or fix packs, forcing you to edit the page again with your new graphic name. Besides what does it matter what you call the image?
The images for the login page are found at the following location, [maximo_home]\applications\maximo\maximouiqeb\webmodule\webclient\login\images. I am using the new iot18 skin so the image I wanted to replace is mx_icon_iot18.png. Rename the existing mx_icon_iot18.png image to something like mx_icon_iot18_original.png so you can return to it should you wish to at some point. Copy your new graphic to the location above and rename it to mx_icon_iot18.png. Note that you will have to rebuild and deploy the EAR before you can see the new graphic.
Now comes the part that was causing my squished image mentioned earlier. If you deploy the EAR now your new graphic may look off unless it happens to conform to the aspect ratio of the original graphic. If, like mine, your image does not there is one more step.
We need to modify the login.css and change the width and height to match our new graphic. You will need to modify the login.css for your particular skin. Again, I am using the iot18 skin so, for me, I will choose the login.css file found at [maximo_home]\applications\maximo\maximouiqeb\webmodule\webclient\css\iot18. Toward the bottom of the file look or search for the header img.prodIcon.
Replace the ??? with the width and height of your particular graphic. You may also increase or decrease the size here just be mindful to keep the same aspect ratio so your image still looks sharp.
You will need to build and deploy a new EAR to see your changes.