Ok, setting this up works well with not just tech icons, but also wonder splashes, LH pcx's, etc.
This is done with Adobe Photoshop Elements which came with my pc. Hopefully it's the same or similar enough on your version of Photoshop.
I'm sure you're aware of some of these things but I thought I'd make it comprehensive for anyone else who wants to use this info.
1. First, take a pic of the right size you want to convert to the proper format. For tech icons I believe it is 128 x 128 pixels. I usually start with jpeg images, but other formats are fine. In the menu, go to Image-Mode-Indexed Color... and 'click' that. Notice how currently RGB Color is checked off. This is the current format of jpeg images. If it's already checked off as Indexed Color you can first check it as RGB Color, then go back to the menu and start this step with it as it is in the pic below.
2. After you select 'Indexed Color', it should bring up the Indexed Color Box, as in the picture below. It will only bring this box up if the pic was previously checked off as something other than indexed color, as mentioned in step 1. With the Indexed Color Box open, go to the forced menu, as in the pic, and select 'Custom' as shown.
3. Selecting 'Custom' brings up a blank palette. Change the first two colours in the palette as shown by 'clicking' the empty spot and selecting your desired colour. The colours I used were FF00FF for the first, and 00FF00 for the second. Then hit 'OK' to close that screen and return to the Indexed Colour Box. Then it'll show 'Custom' selected under the 'Forced' part of the box. Hit 'ok' in the Index Color Box to close it.
4. The new palette should appear as in the pic below. Notice how the colours I selected under forced are part of the palette in the first and second position. The third colour, the blue, I added without showing you but isn't important, just the first and second.
5. Click 'OK' to close the palette in it's new form. Now you'll see if you go to the menu that your pic is ckecked as Indexed Color, as in the pic below. That's how it should be.
6. Next just go to 'Save As' in the menu:
7. And 'Save As' a PCX format pic, under whatever name you want your new icon. And you're done!
8. From then on, any pics you want to convert to 256 Colour Indexed Color from RGB Color, it should bring up the Indexed Color Box with your 'Custom' Colours already set under Forced, as in the pic below, and all you have to do is hit 'ok' to see the new palette, which you can close with another 'ok'. Make sure it says 256 under colours for any PCX you make, as in the pic.
9. Finally, any time you want to double check your palette to make sure your two unused colours (called 'transparency colours') are in the palette, and everything's ok, just go to Image-Mode-Color Table... as in the pic below, and double check your palette before saving.
You can use the above method for many types of modified pcx's in the game. Just make sure that the new icon is in the same pixel size that the originals in the game are, and that you save in a 256 colour pcx with the first 2 colours unused, being devoted to transparency.
Hope that helps in any way.
