Strange question, but.. how big is too big? I mean really?  Im trying to render a scene, not really that difficult when 3/4 of the way through, a big error box pops up and says you dont have enough memory to render this.  So I go and look at the texture I am using on the character and its 4000x4000.  Do they really have to be that big?  I have no idea, so I am asking is that necessary?

you can set the max texture size in the render settings to help with the memory error.

How big is too big depends on the type of a rendering you're making.  Think about how many image pixels will your character cover.

A face closeup on a large image, especially if it's for a print and you want fine detail, 4000x4000 is not too much.

If the whole character is covering about 300x200 pixels on the image, even 1000x1000 may be too big.

thanks Connie, It just seems that certain characters crash poser when ever I am doing over a 1500xsomething render.  Its very frustrating because when I go back to make changes, I loose all the textures because poser states there isnt enough memory to reload them.  I have a 2gig dual core machine too.

It depends on what you are rendering.

Let us say you are rendering a face. The face has a texture map of 4000x4000.

The size of your entire image is 2048x2048, and the face takes up half of the image, you could drop that texture map down to 1024x1024 without losing too much detail.

In other words, if your entire image is 2048x2048, you have just over 4 million pixels. Your image map has 160 million. So there is no way that 160 million pixels will fit into 4 million pixels.

When you reduce your texture map, use the following sizes:
512x512 or 1024x1024 or 2048x2048.

The PC will render images in the sizes more efficiently than say an image of 2000x2000, because those size work better with the internal calculator of the render engine.

Good to Know, thank you.