Making a shield for Arduino Due... any tips or ideas

After the success of 3 small PCB's I made last year (all worked :o ) I would like to make a shield for my Due. I also prefer connecting with male pins and all the Due pins are female as I exclusively use Dupont female <--> female connections.

A large project of mine has several devices and it's a real pain to wire up with multiple SPI, I2C etc, etc.

At the moment I have :-

Multiple 3v3 5V and GND power rails.

2x11 pin connector for OV7670 parallel FIFO camera that maps the parallel pins to port C1-C8. If the camera is not used the pins it nominates as using are easily accessed. With this, a camera can be plugged in and tested in seconds.

2 1x9 C1-C9 port connectors.

2 1x9 C12-C20 port connectors.

The above makes it easy to wire a device that needs a parallel interface. Also, gives easier sequential access to pins in single rows. Both have potential access to 9 sequential port pins.

Built in pins for micro SD card breakout (GND 5V MISO MOSI SCK CS(4)).

Built in pins for RTC1307 card (GND 3V3 SDA SCL SQW 32K)

DIP socket area for adding EPROM (8 pin) with optional pullup on CS via jumper, optional capacitor between 3v3 and GND.

5 SPI hubs with (GND 3V3 5V MISO MOSI SCK CS) the CS lines are nominated however if not used for SPI the CS lines can be used as usual. Put a 5V option on the pin as some displays prefer 5V and don't have MISO connected.

5 I2C hubs with (GND 3V3 SDA SCL) and option to put a pullup on SDA and/or SCL via jumpers.

Have a 1x8 row of pins for SPI display (GND 3V3 5V MOSI SCK DC RST CS). In most cases the MISO would have no connection... maybe I should include it for flexibility? The pins nominated for DC, RST and CS can be used normally if SPI display not used.

All the pins on the bottom (ie. A0 -> A7 and A8 -> CANTX) are broken out with S/G/3V3.

ATM I have no reset on board as the original reset button is accessible.

Was wondering, where I offer 5V or 3V3 for some would I be better off having a jumper or micro switch (thus making it impossible) to connect both at the same time?

All 3V3 and 5V pins are square.

Routing of SPI lines will try and avoid unneeded complications and be as short as possible.

I usually use a pour on the back for GND and make the 3V3 and 5V lines a bit thicker.

I read somewhere that basically said "fill the board"... allow for "optional" parts like caps near IC's and spaces for "air wires". Optional status led ? Might make a socket that breaks out pin 13 with a resistor that would allow any standard PC "led" connector to be clicked onto the board.

Will probably add easy access to SPI pins for a logic analyser (even though I don't have one).

Might be worth setting a space aside for Bluetooth and or wi-fi as most of those seem to have standard connectors?