resizing for threadless

I'm trying to make a desing for threadless.com. The problem is resizing my desing for the submission. There is a four color limit so the best I've been able to do is pick "nearest neighbor" for resample image. This keeps it at four colors, but it looks really bad. Anything else I've tried blures design and makes it too many colors. Does anyone have any other suggestions?
thanks

I'm not sure I understand....
(probably because I'm too old to know what "threadless" is)
<<< update: I looked at the site and now I understand>>>>

They want a maximum of 4 color either process color (CMYK) or 4 "spot" colors

To create a new spot channel:
1. Choose Window > Channels to display the Channels palette.
2. To fill a selected area with a spot color, make or load a selection.

Now do one of the following to create a channel:
* Ctrl-click (Mac OS: Command-click) the New Channel button in the Channels palette.
* Choose New Spot Channel from the Channels palette menu.

You will see a new Channel icon appear at the bottom of the Channels Palette, with your selection

If you made a selection, that area is filled with the currently specified spot color.

You'll need to assign a color to this channel.
* Click the color box, and choose a color (Select from any of the color systems included with your Photoshop program. If you create your own custom color, don't worry, the screen printer can mix up the ink color you need.

Converting existing channels to spot channels:

If you have edited and modified one of the existing Process (CYMK) channels for use as a Spot color, then do one of the following:
* Double-click the alpha channel thumbnail in the Channels palette.
* Select the alpha channel in the Channels palette, and choose Channel Options from the palette menu.
2. Rename the channel (Again this is important)
3. Select Spot Color
4. Click the color box, choose a color in the Color Picker dialog box, and click OK. Do NOT pick the same color again. You don't want two films of the same color.