Yes that is completely normal and nothing to be alarmed about... as was posted by Medzinatar, It's just 3Delight running tdlmake to optimize the textures, bumpmaps and etc as part of the normal process of rendering...

When it shows a large number if images to optimize you have to keep in mind that each prop, figure, or character you load into a scene may have one texture or many and the more complex the item the more likely it will have a number of maps assigned to it (for example a vicky figure might have maps for head, body/limbs, eyes, corneas, brows, lashes, etc... plus bump maps and trans-maps as well for every copy of that figure you use... and then there are the maps for her hair, clothes items and etc) rather than a single image map.

If you had 20 items in the scene each using 5 textures then you would potentially have 100 image maps that tdlmake has to process. Tdlmake has to optimize each of these to prep the render which is what leads to that message...

I often do test renders as I work on setting up a new scene, so that I can make sure that things are coming together the way I want them to, and will frequently get this message pop-up when the render starts...